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HANDBOOK OF THE MEM SERIES.

Edited by J. CHALMERS MORTON,

EDITOR OF THE "AGRICULTURAL CYCLOPyEDTA ; " THE "AGRICULTURAL GAZETTE;

THE "farmer's calendar;" the "farmer's almanac;"
"handbook of the dairy;" "farm labourer," etc.

MESSRS. MACMILLAN & CO.'S
PUBLICATIONS.

FIEST PEINCIPLES OF AGEICULTUEE,

By henry tanner, F.C.S.

Professor of Agricultural Science, University College, Aberystwith ; Examiner in the
Principles of Agriculture, under the Government Department of Science.

18mo. Is.

" A manual which ought to be in the hands of every farmer, and in use In every school
in our agricultural districts. . . . It is clear, concise, exceedingly readable, but in-
tensely practical, and cramful of valuable and reliable facts."— Live Stock Jownal.

ELEMENTS OF AGEICULTUEAL SCIENCE.

BY THE SAME AUTHOR.

Fcap. 8vo. [Immediatehj.

THE ABBOTT'S FAEM;

OK,

PRACTICE WITH SCIENCE.

BY THE SAME AUTHOR.

Crown Svo. 3-?. Qd.

"The story is well told. . . . Professor Tanner gives valuable advice as to the
growth of roots, the best means of helping labourei-g, hints as to apprenticeship, &.c,,
which commend themselves to special notice." — The Field.

MACMILLAN & CO., LONDON, W.C.

HANDBOOK OF THE FARM SERIES

Edited by J. CHALMERS MORTON.

THE

CHEMISTRY OF THE FARM.

BY

E. WAEINGTON, F.C.S.

■■^irFOE^'^b^

LONDON:
BRADBURY, AGNEW, & CO., 9, BOUYERIE STREET.

1881.

4^

The preseut Volume is the first of a series of Jive — the others
discussing the Live Stock and the Crojis of the Farm, the Soil
and its Tillage, and the Equipment of the Farm and the Estate.
Each book will be complete in itself, and the whole will form a
Handbook of the Faiin adapted to the wants of the teacher and
the student of agriculture. The remaining volumes of the series
will appear as they are ready. Among the names of the writers
engaged on them are W. T. Carrington, G. Murray, T. Bowick,
G. Gilbert, S. Spencer, W. Burness, J. C. Morton, and others.

J. C. M.

\)A

PEEFACE.

TiiEEE is perhaps scarcely any need for an
apology in bringing ont a new work on a brancli
of science wliich develops at sncli a rapid rate as
Agricultural Cliemistry. In the case of such a
science the lapse of a few years must find any
text-book, however good, more or less deficient in
important particulars. We might, however, urge
a special reason on the present occasion, namely,
the scarcity of books on farm chemistry in the
English language. Our countrymen have indeed
conducted many notable investigations on the
chemistry of the soil, plant, and animal, and the
papers containing tlieii- results rank among the
classics of our scientific literature ; but of text-
books for students, discussing agricultiu'al che-
mistry as a whole, we have scarcely any, and none

VI PREFACE.

perhaps in whicli the present aspects of the science
are at all adequately represented.

The present little book is primarily intended to
supply a demand, which we believe is gradually
arising, for the teaching of agricultural science in
our schools ; it is intended as a small text-book
for the use of teachers, expressing briefly, and we
hope clearly, the principal facts which form the
basis of agricultiu'al chemistry. Though intended
thus in a special manner for teachers, we hope it
may prove useful to all who may wish to become
students of the subject. When used by a teacher
the matter should be taken a little at a time, and
enlarged upon in the course of the lesson. Parti-
cular opportimity for enlargement is fui'uished by
the tables contained in the book ; the facts they
represent, being self-evident on a consideration of
the figures, are often very slightly alluded to in
the text, but are left to the observation and study
of the reader.

It is assumed that those who use this book will
have a general acquaintance with the facts of ele-
mentary chemistry ; a knowledge of these must

PREFACE. VU

precede any study of tlie particular cliemistry of
plants or animals. It is also very desirable that
something should be known of the structure, and
processes of life in plants and animals ; such
knowledge is quite essential for clear ideas on
agricultural science. The teacher or student thus
furnished will be the one best able to make use of
the special information which it is the object of the
following pages to convey.

It may perhaps be of service to mention a few
books which will be found useful by the student.
Among works on plant physiology we may name
the Text-Books of Botany by Thom6, and by Prantl
(Vine's translation), and the still more elementary
work by Mcl^ab. "How Crops Grow" is an
excellent work, but is, we fear, out of print.

In animal physiology Huxley's Elementary
Lessons may be particularly recommended.

"How Crops Feed" is an excellent work, chiefly
devoted to the chemistry of soil; it is now
somewhat old.

There are also two capital little German works
by E. Wolff, embracing the whole subject of

Vlll PREFACE.

agricultural chemistry ; these are, " Praktische
Diingerlehre," and *' Landwirthschaftliche Fiitter-
ungslehre."

The best English work on agricultural chemistry-
exists as yet only in detached papers. The
numerous reports containing the Eothamsted in-
vestigations on the chemistry of crops and
animals will be found chiefly in the Journal of
the Eoyal Agricultural Society.

R. W.

May, 1881.

CONTENTS

CHAP. VAGH

I. — Plant Gkowth 1

II. — Sources of Plant Food 13

III. — Manures 23

IV.— Crops 37

V. — Rotation of Crops 50

VI. — Animal Nutrition . . . . . . . .60

VII. — Foods 71

VIII. — PiELATION OF FoOD TO AnIMAL REQUIREMENTS . . . 95

IX. — Relation of Food to Manure ...... 109

X.— The Dairy 117

THE

CHEMISTEY OF THE FAKM

CHAPTER I.

PLANT GROWTH.

The Constituents of Plants. —Water — The comlDustible elements of vege-
table matter — The proportion of ash constituents in various parts of
plants — The essential and non-essential elements of the ash — Com-
position of a crop of grass. Function of the Leaves. — Assimilation of
carbon from the air — Formation of vegetable substance — Plant re-
spiration— The transpiration of water. Function of the Roots. — Ab-
sorption of ash constituents and nitrogenous matter from the soil —
The excretion of useless matter by the plant — The part played by ash.
constituents. Germination. — General character of seeds — The con-
ditions and processes of their germination. Plant Development. —
Annual plants — the order in which plant constituents are assimilated
— Biennial and perennial plants — the storing up of food for a second
season — spring sap rich in sugar.

The first step towards a knowledge of plant chemistry
must be an acquaintance with the materials of which
plants are built up.

The Constituents of Plants The most abundant

ingredient of a living plant is water. Many succulent
vegetables, as turnips and lettuce, contain more than 90
per cent, of water. Timber felled in the driest time
seldom contains less than 40 per cent, of water.

I B

2 THE CHEMISTRY OF THE FARM.

If a branch of a tree is burnt, the gi-eater part is con-
sumed and passes away in the form of gas, but there is
left behind a small quantity of white ash. The same
happens if any other part of a plant is burnt. The con-
stituents which form the dry matter of plants may be thus
conveniently divided into two classes — the combustible
and the incombustible.

The combustible part of plants is made up of five
chemical elements — carbon, oxygen, hydrogen, nitrogen,
and sulphur; without these no plant is ever produced.
Carbon generally forms about one-half of the dry com-
bustible matter of plants. Nitrogen seldom exceeds 4 per
cent, of the dry matter, and is generally present in much
smaller amount. Sulphur is still smaller in quantity. The
remainder is oxygen and hydrogen.

The carbon, hydrogen, and oxygen form the cellulose,
lignose, pectin, starch, sugar, fat, and vegetable acids which
plants contain. The same elements united with nitrogen
form the amides and alkaloids ; and further united with
sulphur the still more important albuminoids, which are
essential constituents of all plants.

The incombustible or ash constituents form generally
but a small part of the plant. The timber of freely-grow-
ing trees contains but 0.2 — 0.4 of ash constituents in 100
of dry matter. In seeds free from husk the ash is gene-
rally 2 — 5 per cent. In the straw of cereals 4 — 7 per
cent. In farm roots 4 J — 8 per cent. In hay 5 — 9 per
cent. It is in leaves, and especially old leaves, that the
greatest proportion of ash is found ; in the leaves of root
crops the ash will amount to 10 — 25 per cent, of the dry
matter.

The incombustible ash always contains five chemical

PLANT GROWTH. 3

elements — potassium, magnesium, calcium, iron, and phos-
phorus, besides sulphur alread}^ mentioned. Iron is present
in only very small quantity. These five elements, though
forming a very small portion of the plant, are indispensable
to its life. Besides the elements just named, an ash will
generally contain sodium, silicon, and chlorine, with fre-
quently manganese, and perhaps minute quantities of
other elements. The supplementary elements just named
are not apparently essential to plant life, though some of
them discharge useful functions in the plant.

The metals above-named occur in the plant as salts,
being combined with phosphoric, nitric, sulphuric, and
various vegetable acids, of which oxalic, malic, tartaric
and citric acid are the most common. The metals are
also sometimes present as chlorides. Phosphorus occurs
in the form of phosphates ; silicon is present as silica.
Sulphur occurs partly as sulphates, and partly as a
constituent of albuminoids. In the ash of plants the
nitrates, and the salts of the vegetable acids are found in
the form of carbonates.

It is common to speak of the combustible ingredients
of a plant as "organic," and the incombustible ingredients
as "inorganic." This distinction is scarcely acourate, as
those ash constituents which are indispensable parts of
plants have, during the plant's life, as much right to be
called "organic" as albumin or cellulose.

In the following table will be found the average com-
position of a crop of meadow grass weighing 5 tons when
cut, and producing IJ ton of hay ; this will illustrate
what has just been said as to the constituents of plants.
Further information as to the composition of crops will be
found on page 38.

THE CHEMISTRY OF THE FARM.

COMPOSITION OF A CROP OF ^lEADOW GRASS.

Water ....

. 8,378 lb.

Carbon .

1315 \

Hydrogen .

Nitrogen

Oxygen and Snlphnr .

■^^g > Combustible matter .

. 2,613 lb.

1105 )

Potash .

56. 3 N

Soda ....

11.9

Lime

28.1

Magnesia .

10.1

Oxide of iron .
Phosphoric acid .

.9
12.7

Ash

209 lb.

Sulphuric acid

10.8

Chlorine .

16.2

Silica .

57.5

Sand, &c. .

45/

Total crop

. 11,200 1b.

Plants obtain the elements of which they are built np
partly from the soil, and partly from the atmosphere.
From the soil they obtain, by means of their roots, all
their ash constituents, all their sulphur, and nearly the
whole of their nitrogen and water. From the atmosphere
they obtain, through the instrumentality of their leaves,
the whole, or nearly the whole, of their carbon, with pro-
bably small quantities of nitrogen and water.

Function of the Leaves. — The source of vegetable
carbon is the carbonic acid gas present in the atmosphere.
Carbonic acid gas passes more readily through the cuticle
of a plant than do the nitrogen and oxygen which make
up the bulk of the atmosphere. The carbonic acid thus
absorbed is decomposed within the chlorophyll cells of the
plant under the influence of light, oxygen being evolved,
and the carbon retained by the plant. All green parts of a
plant probably share in this action, but it is pre-eminently

PLANT GROWTH. 5

the function of the leaves. The decomposition of carbonic
acid does not proceed in darkness, or at a very low tem-
perature. The rajs of light most active in effecting the
decomposition are the yellow and orange rays ; the blue,
violet, and dark red rays of the spectrum have scarcely
any influence.

The oxygen gas given off by a green plant exposed to
light is equal in volume to the carbonic acid decomposed,
so that apparently the whole of the oxygen contained in the
carbonic acid is returned to the atmosphere ; the reaction
is, however, really more complicated, as water is probably
decomposed at the same time as the carbonic acid.

The exact nature of the reaction which takes place
when carbonic acid is decomposed in the chlorophyll cells
is still unknown. Starch, composed of carbon and the
elements of water (CqUkjO^), is undoubtedly among the
earliest products. Starch being an insoluble substance is
converted into sugar (glucose) for the nourishment of
distant parts of the plant, to which it is conveyed by the
movement of the sap. In parts where growth is taking
place, and new cells are being formed, the sugar of the
sap is converted into cellulose, the substance which forms
the cell walls, and of which the whole structure of the
plant primarily consists. The conversion of starch into
sugsiv and cellulose presents no chemical difficulties, as all
these substances are carbo-hydrates, that is they are
composed of carbon and the elements of water.

The formation of albuminoids in the plant is not at
present understood ; we can onh'^ say that they are con-
stituted out of the carbo-hydrates and some of the simple
nitrogenous substances, most probably amides, present in
the sap.

C THE CHEMISTRY OF THE FARM.

The vegetable acids in a plant are probably formed by
oxidation ; most likely by the oxidation of some of the
carbo-hydrates.

The fatty matter of a plant may be formed from carbo-
hydrates ; or possibly from the splitting up of albuminoids.

We have just referred to oxidation as taking place in
the plant. This is always going on in the interior during
life, and as a result the plant is continually consuming a
small quaiitit}^ of oxygen, and giving out a small quantity
of carbonic acid, an operation precisely similar to animal
respiration. This action is not readily perceived during
the day-time, being hidden by the opposite action of the
chlorophyll cells, which absorb carbonic acid and evolve
oxygen. If a plant is placed in darkness the respiratoiy
action becomes manifest. The oxidation of matters already
formed is an important means for the production of new
bodies.

The decomposition of carbonic acid by green plants
during daylight is of the utmost importance in maintain-
ing an atmosphere suitable for the respiration of animals.
An animal in breathing inspires atmospheric air ; it expires
air in which a part of the oxygen has been replaced by
carbonic acid; the result of animal life is thus to accu-
mulate carbonic acid in the atmosphere. Such accumula-
tion would be injurious to health, but is prevented by the
growth of plants. It has been calculated that an acre of
forest, producing annually 5755 lb. of dry matter, will
consume the carbonic acid produced by the respiration of
15.4 men.

Besides carbonic acid, plants are apparently capable of
absorbing a small quantity of ammonia through their
leaves. The uncombined nitrogen of the atmosphere is

PLANT GROWTH. 7

not appropriated by plants. When rain occurs after -severe
drought water may be taken up to some extent through
the leaf.

Plants which have no chlorophyll cells, and possess
consequently no green colour, do not decompose carbonic
acid. We have familiar examples of such plants in the
broomrape and dodder of our clover fields, and in the
common fungi. The broomrape and dodder are fed by
the juices of the plant on which they live as parasites.
The fungi derive their carbon from the decayed vegetable
matter in the soil.

Another important function of leaves consists in the
transpiration of water. This transpiration takes place
through small openings in the under side of the leaves,
known as stomata, which have the property of closing in
dry air and opening in moist. Transpiration takes place
only in light ; it will occur abundantly, even in an atmo-
sphere saturated with water, if the plant be only exposed
to sunshine. A small amount of general evaporation, dis-
tinct from transpiration proper, may occur in darkness.
The amount of water evaporated from the surface of a
growing plant is veiy large ; land that has borne a crop is
always much drier than a bare fallow.

The results of transpiration to the plant are most im-
portant, the evaporation of water from the leaves being a
principal cause of the rise of the sap, and the consequent
drawing up of water from the soil containing plant food in
solution.

Function of the Roots. — The roots of a plant are the
organs by which it absorbs water from the soil, and with
this water a variety of food elements are introduced.

8 THE CHEMISTRY OF THE FARM.

The roots take up apparently all the diffusible sub-
stances (those capable of passing through a membrane)
which are present in the water which they draw from the
soil. The plant may thus receive a number of substances
not actually required for its nutrition.

The feeding power of roots is not, however, confined to
the taking up of ready-formed solutions, they are also
capable of attacking some of the solid ingredients of the
soil, which they render soluble and then appropriate. This
important action of roots exists in different degrees with
different plants. The action takes place only at the points
of contact between the rootlets and the particles of the
soil, and is brought about by the acid sap which the roots
contain. This action of roots probably plays an important
part in the supply of phosphoric acid and potash to the
plant, as these substances, especially the former of them,
exist in the soil in difficultly soluble forms, and are rarely
found in solution in the water present in soils.

Besides furnishing the plant with its ash constituents,
the root has the important function of supplying nitrogen ;
this is nearly always taken up in the form of nitrates. A
plant is capable of making use of nitrogen in the form of
nitric acid or ammonia ; it also, according to several ex-
perimenters, is able to assimilate nitrogen when in the
form of urea, uric and hippuric acids, and several other
amide bodies. The facility, however, with which ammonia,
and other nitrogenous substances, are converted into nitric
acid in the soil is so great that nitrates become by far the
most important source of nitrogen at a plant's disposal.
Most plants are unable to assimilate the nitrogenous
humus contained in soil.

The very weak solutions taken up by the roots are

PLANT GROWTH. 9

concentrated in the upper parts of the plant, the water
being rapidly evaporated by the leaves, as already men-
tioned. The essential ash constituents are employed in
the formation of new tissues. The non-essential ash
constituents which have been taken up by the roots are
partly disposed of in a solid form, as a permanent incrus-
tation of the older tissues. The soluble salts which are
not thus disposed of, at first accumulate in the sap, and
are probably more or less removed from the surface of the
leaves and stem by the washing effect of rain.

The deposition of silica upon the external tissues of
wheat, barley, and other graminaceous plants is a familiar
example of the excretion of a non-essential ash constituent.
Silica is also abundant in the old leaves, and in the outer
bark of many trees, and is commonly found as an incrust-
ing constituent of old tissues. Insoluble calcium salts,
frequently the oxalate, are also deposited as incrusting
matters in old tissues. These incrustations are indirectly
of service to the plant, as they tend to harden the tissues
and thus protect them from injury.

Soluble non-essential ash constituents, as chloride of
sodium, are found abundantly in the succulent parts of
plants when such ash constituents have been present in
the soil. They generally diminish in quantity as the
plant matures, and are never stored up in the seed.

The amount and composition of the ash of succulent
plants, as meadow grass, clover, and mangel, is greatly
influenced by the character of the soil, and the manure
applied. The ash of a seed, on the other hand, is very
constant in composition, resulting from the selective
powers of the plant.

Of the particular action of the ash constituents within

10 THE CHEMISTRY OF THE FARM.

the plant little is known. Phosphoric acid and potash are
undoubtedly the most important of the ash constituents ;
they are always found concentrated in those parts of the
plant where cell growth is most active, as, for instance, in
the layer (cambium) between the wood and bark of a tree,
and are abundantly stored up in the seed.

Silica was long supposed to be an essential constituent
of wheat, barley, and other similar plants, and to be the
ingi-edient on which the stiffness of their straw chiefly
depended. It has been shown, however, that maize may
be successfully grown without any supply of silica, and
with no perceptible difference as to the stiffness of the
stem. The grass growing on peat bogs contains scarcely
any silica, though silica is abundant in ordinary hay.

Germination. — The seed is a storehouse of concentrated
plant food, intended to nourish the germ till the root and
leaf are developed. In the seeds of the cereals, and of many
other plants, the chief ingredient is starch. Another class
of seeds, of which linseed and mustard-seed are examples,
contain no starch, but in its place a large quantity of fat.
A seed generally contains a considerable amount of albu-
minoids ; its ash is rich in phosphoric acid and potash.

For germination to take place, moisture, oxygen, and a
suitable temperature are necessary. Under these con-
ditions the seed swells, oxygen is absorbed, a part of the
carbonaceous ingredients is oxidised, heat is developed,
and carbonic acid evolved. During these changes the
solid ingredients of the seed gradually become soluble ;
the starch and fat are converted into sugar; the albu-
minoids are converted into amides — as for instance aspara-
gine, probably also into peptones. With this supply of

PLANT GROWTH. 11

soluble food the radicle and plumule are nourished ; they
rapidly increase in size, emerge through the coats of the
seed, and, if the external conditions are suitable, soon
commence their separate functions as root and leaf. The
process of germination may be easily studied in the
ordinary operation of malting barley.

Seeds buried too deeply in the soil may not germinate
for lack of oxygen. Or if germination takes place the
plumule may fail to reach the surface, the store of food in
the seed being exhausted before the layer of soil is pene-
trated, and daylight reached. The smaller the seed, the
less, as a rule, should be the depth of earth with which it
is covered.

Plant Development. — The development of the plant
after germination follows a regular course. With an
annual, which produces seed and dies during the first
season, we have first a great development of root and
leaf, which collect and prepare materials for growth ; next
comes the formation of a tiower stem ; and lastly, the pro-
duction of flower and seed; after which the plant dies.

The materials furnished by the root preponderate in the
young plant ; but as the plant matures, the proportion
of carbon compounds derived from the action of the
leaves steadily increases. A cereal crop contains at the
time of full bloom all the nitrogen and potash which is found
in the mature crop ; the assimilation of phosphoric acid
continues somewhat later ; the increase of carbon and silica
proceeds as long as the plant is in a green state.

When seed formation begins an exhaustion of the other
parts of the plant sets in, starch, albuminoids, phosphoric
acid and potash being transferred from the root, leaf, and

12 THE CHEMISTRY OF THE FARM.

stem, and stored up in the seed. If the season is a good
one, and the development of the seed fully accomplished,
the straw of the crop is left very thoroughly exhausted ;
while in a bad season it will retain far more of the materials
acquired during growth. For the same reason straw cut
"while the crop is still green is far more nutritive than
when perfect ripeness has been attained.

With a biennial or perennial crop the case is somewhat
different. The first development of root and leaf is the
same as in an annual ; but towards the end of summer
there is a storing up of concentrated plant food in the root
or stem to serve for the commencement of growth in the
following spring. In a biennial root crop, the turnip for
instance, the root attains a great size in autumn, the leaves
dying after transferring to the root their most important
constituents. The next season the root throws up a
flower stem, and the store of matter accumulated during
the preceding autumn is consumed in the production of
seed. With the production of seed the root is exhausted
and the plant dies.

In trees plant food is stored up at the end of summer
in the pith, the pith rays, and in the layer between the
•wood and bark. The leaves which fall in autumn have
lost nearly all their starch, albuminoids, phosphoric acid
and potash, these having been transferred to the stem.
By the action of the sun in spring-time the new buds
swell, the sap rises, the starch and other matters deposited
in the wood during the previous autumn are re-dissolved,
and employed at once for the production of new growths.
The sugar found in maple sap during spring results from
the transformation of starch stored up in the preceding
autumn.

CHAPTER ir.

THE SOURCES OF PLANT FOOD.

The Atmosphere. — The carbonic acid, ammonia, and nitric acid which it
supplies — The quantity of combined nitrogen and chlorides contained
in rain. The Soil. — Its origin — Proj)erties of sand, clay, calcareous
matter, and humus ; their relation to water and heat — The plant food
contained in soil, its quantity, and condition — Losses by drainage —
The absorptive power of soils — Influence of tillage, drainage, and
burning.

The Atmosphere. — We have already stated that the
whole of the carbon of plants is obtained from the carbonic
acid present in the atmosphere ; 10,000 volumes of air
contain about 3J volumes of carbonic acid, or about 1 lb.
of carbon in 3500 cubic yards of air. This small amount
is made sufficient by the action of winds, which bring an
enormous quantity of air in contact with both soil and
plant.

The atmosphere also contains a very small and variable
quantity of ammonia. Schloesing found from 1 lb. in
6,000,000 cubic yards, to 1 lb. in 119,000,000 cubic yards.
The quantity is greatest, according to the same experi-
menter, in warm southerly winds. The ammonia of the
air is directly absorbed by plants to a very small extent, it
is rendered available chiefly through absorption by the
soil, and by means of rain, which brings it in solution to
the earth.

,14 THE CHEMISTRY OF THE FARM.

The atmosphere also furnishes a small amount of nitric
acid. The nitrogen and oxygen of the atmosphere com-
bine under the influence of electric discharges, nitrous
acid being formed ; tjiis is converted into nitric acid by
the action of ozone, or peroxide of hydrogen. This forma-
tion of nitric acid in the atmosphere is the only original
source of combined nitrogen on our globe the existence of
which has been placed beyond dispute. Nitric acid may
also be formed in the atmosphere by the oxidation of
ammonia by ozone and peroxide of hydrogen.

The total amount of nitrogen, in the form of ammonia
and nitric acid, annually carried to the soil by rain, varies
in different years and places. The average of many experi-
ments on the continent gives 10.23 lb. of nitrogen per acre.
The average of two years' experiments at Rothamsted gave
7.29 lb. The continental average is probably rather above
the truth for the open country, many of the determinations
having been made near towns.

Rain also furnishes small quantities of alkaline chlorides,
especiall}'- in the neighbourhood of the sea ; sulphates are
also present. At Cirencester the chlorides in the rain are
on an average equal to about 53 lb. of common salt per
acre per annum ; at Rothamsted in Hertfordshire the
quantity is about 22 lb.

The Soil. — All soils have been produced by the dis-
integration of rocks, generally through the prolonged
action of water, air, and frost. The character of a soil
largely depends on the character of the rock from which
it has been derived. Primitive and igneous rocks yield
soils rich in potash ; fossiliferous rocks produce soils rich
in phosphoric acid. The principal ingredients of soils are

THE SOURCES OF PLANT FOOD. 15

sand, clay, carbonate of calcium, and humus ; as each of
these preponderate the soil is said to be sandy, clayey,
calcareous, or peaty.

Sand is either composed of pure quartz (silica), or con-
sists of fragments of more complex minerals — mica, for
example. When the former is the case, the sand will
supply no plant food ; but in the latter case the gradual
decomposition of the mineral will slowly increase the ash
constituents available for the plant.

Clay is a silicate of aluminium, produced by the decom-
position of felspar and other silicates ; if absolutely pure it
would furnish nothing to the plant ; it always, however,
contains some potash, and frequently a considerable quan-
tity. Clay has the important 23roperty of absorbing and
retaining phosphoric acid, ammonia, potash, lime, and
other substances necessary for plant nutrition.

The calcareous matter of soils supplies lime to the
plant ; limestone also generally contains phosphoric acid.
Carbonate of calcium is beneficial to the soil in many
ways. It preserves the particles of clay in a separate
coagulated condition, thus making heavy soils friable and
pervious to water. It enables clay to exercise its absorbent
power on various salts, which would otherwise escape its
action. It also promotes the decomposition of vegetable
matter, and the formation of nitrates in the soil. The
presence of some salifiable base is essential for the per-
formance of the chemical operations belonging to a fertile
soil ; the salifiable bases usually present are either carbo-
nate of calcium, or the alkalis derived from the decom-
position of silicates.

The humus, or decayed vegetable matter of soils, has its
origin in the dead roots, leaves, &c., of a previous vegeta-

IG THE CHEMISTRY OF THE FARM.

tion. It is the principal nitrogenous ingredient of soils.
A black soil, rich in humus, is sure to be also rich in
nitrogen ; a soil destitute of humus will contain scarcely
any nitrogen. The fertility of virgin soils is largely due
to the nitrogenous humus which they contain.

Of all soil ingredients sand has the least, and humus
the greatest capacity for retaining water. Light sandy
soils thus suffer most from drought, while applications of
farmyard manure, or the ploughing in of green crops,
increase the water-holding power of a soil by increasing
the proportion of humus. The capillary power of soil,
by which water is raised from the subsoil to the surface
in dry weather, is least in open sandy soils composed of
coarse particles, and greatest in the case of loam or clay.

Dark-coloured soils absorb the greatest amount of heat
from the sun's rays, and light-coloured soils least. The
presence of humus is thus favourable to soil warmth.
Quartz sand is an excellent conductor of heat ; chalk is a
bad conductor. A soil rich in sand will thus be warmed
or cooled more rapidly, and to a greater depth than a soil
containing but little sand. Water has a very considerable
effect in cooling a soil, partly from its high specific heat,
and partly from the immense consumption of heat during
its evaporation. A wet soil is always colder than a dry
one. The drainage of wet land will thus result in a
gi-eater warmth of the surface soil, and consequently an
earlier growth in spring.

The proportion of plant food present in soils is very
small, even when the soil is extremely fertile. The surface
soil (first 9 inches) of a pasture may contain when dry 0.25
of nitrogen per cent., while soil of the same depth from a
^ood arable field may yield 0.15 per cent., and a clay

THE SOURCES OF PLANT FOOD. l7

sub-soil 0.05 per cent. A good surface soil may contain 0.20
per cent, of phosphoric acid, or not unfrequently a smaller
quantity. Potash varies much, rising to 1.0 per cent, or
more in some clay soils, but being generally much smaller.

The weight of soil on an acre of land is, however, so
enormous, that small proportions of plant food may amount
to very considerable quantities. Nine inches' depth of
arable soil (clay or loam) will weigh, when perfectly dry,
about 3,000,000 or 3,500,000 lb. A pasture soil will be
lighter, the first 9 inches weighing when dried and the
roots removed about 2,250,000 lb. Supposing, therefore,
a dry soil to contain 0.10 per cent, of nitrogen, phosphoric
acid, or potash, the quantity in 9 inches of soil will be
from 2250 lb. to 3500 lb. per acre.

A large part of the elements of plant food contained in
soils is present in such a condition that plants are unable
to make use of it. A soil may contain many thousand
pounds of phosphoric acid or of nitrogen, and yet be in a
poor condition ; while a small dressing of readily available
food, as superphosphate or nitrate of sodium, may greatly
increase the fertility.

The nitrogen contained in humus is not in a condition
to serve as a general plant food ; cereal crops are appa-
rently unable to appropriate it; leguminous crops, how-
ever, possibly assimilate some humic matters. By the
action of a minute Bacterinr)i present in all soils, humus
and ammonia are oxidised, and their nitrogen converted
into nitric acid. Nitrification only takes place in moist
soil, sufficiently porous to admit air. It is also necessary
that some base should be present with which the nitric
acid may combine : this condition is usually fulfilled by the
presence of carbonate of calcium. Nitrification is most
I c

18 THE CHEMISTRY OF THE FARM.

active at summer temperatures ; it ceases apparently near
the freezing point.

The fragments of rock present in soil, as stones, gravel,
and sand, are as a rule of little value to a plant, the
elements of plant food which they contain being in too in-
soluble a condition to be attacked by the roots. These
fragments of rock may however be slowly decomposed by
the mechanical action of frost, and by the chemical action
of water, and their contents thus gradually made available
to the plant. The solvent power of the water in a soil is
greatly increased by the carbonic acid, and perhaps also
by the humic acid it holds in solution. Water containing
carbonate of calcium in solution is especially capable of
attacking silicates.

If water is allowed to drain through a soil it carries with
it a part of the readily soluble matter which a soil con-
tains. The substances chiefly removed by the water will
be the nitrates, chlorides, and sulphates of calcium and
sodium. When heavy rain falls these substances are
washed into the subsoil, and partly escape by the nearest
outfall into the springs, brooks, and rivers. The loss of
nitrates from highly manured land during a wet season is
very considerable. When dry weather sets in evaporation
takes place at the surface of the soil, the water of the sub-
soil is slowly brought again to the surface by capillary
attraction, and the salts it contains are concentrated once
more in the upper soil, forming in some rare instances a
white crust of salt upon the surface. Capillary attraction
has little influence in the case of Sandy soils.

Of these readily soluble salts the nitrates are of the
greatest importance as plant food. The quantity of
nitrates in a surface soil will vary greatly, depending on

THE SOURCES OF PLANT FOOD. 19

the richness of the soil in nitrogen, the previous conditions
as to temperature and moisture, the extent of recent
washing by rain, and on whether the soil is or is not
under crop. Where a crop is growing the nitrates will
be kept nearer the surface, the evaporation of water from
a growing crop being far greater than from a bare soil.
The nitrates will also be constantly taken up by the roots,
and employed as plant food. The loss of nitrates by
drainage is thus far less when the land is under crop than
in the case of a bare fallow.

Phosphoric acid, potash, and ammonia are very rarefy
found in drainage water. If a solution containing phos-
phoric acid, potash, or ammonia is poured on a sufficiently
large quantity of fertile soil, the water which filters through
will be found destitute of these substances. This retentive
power of soil for phosphoric acid, potash, &c., is of the
utmost importance in agriculture. The action is a com-
plex one. All salts are doubtless retained to some extent
by soil through mere mechanical adhesion; salts, thus
feebfy retained, as nitrates and chlorides, can be easily
removed by washing with water. Other substances are,
on the contrary, retained by chemical affinity ; these are
not removed by washing, or but to a small extent. The
ingredients of the soil which exercise a chemical retentive
power are the hydrates of ferric oxide and alumina, the
hydrous silicates of aluminium, and humus.

Ferric oxide is a common ingredient of soils ; to it the
red colour of many soils is owing. To the presence of
ferric oxide the retention of ^phosphoric acid is chiefly
due, an insoluble basic phosphate of iron being produced.
Alumina acts in the same manner. Ferric oxide and
alumina have also a retentive power for ammonia and

c 2

20 THE CHEMISTRY OF THE FARM.

potash, but the compounds formed are more or less de-
composed by water. To the hydrous silicates the perma-
nent retention of potash and other bases is probably chiefly
due. Humus has a great absorbent power for ammonia.
Other bases, as magnesia and lime, are also retained by
soil, but in a less powerful manner than are potash and
ammonia.

Soils destitute of carbonate of calcium take up very
little potash or ammonia when these are applied as salts
of powerful acids, as for instance, the chlorides, nitrates,
and sulphates. When carbonate of calcium is present the
potassium or ammonium salt is decomposed, the base is
retained by the soil, while the acid escapes into the
drainage-water united with calcium. The addition of
carbonate of calcium may thus greatly increase the re-
tentive power of a soil for bases.

The fertility of a soil is nearly connected with its power
of retaining plant food. Sandy soils, from their small
chemical retentive power, and free drainage, are of small
natural feilility, and dependent on immediate supplies of
manure.

There can be little doubt that the plant food contained
in soil which is capable of being taken up by roots, exists
either in solution, or in the states of combination just re-
ferred to — that is in union with ferric oxide, hydrous sili-
cates, and humus. Different crops have very different
powers of attacking these various forms of plant food.

The operations of tillage and drainage serve in several
ways to increase the amount of plant food which is at the
disposal of a crop.

By tillage the surface soil is kept in an open porous
condition, favourable for the distribution of roots. By

THE SOURCES OF PLANT FOOD. 21

this means also capillary attraction is diminished, and the
land consequently suffers less from drought ; the water-
holding power of the surface soil is also increased. A more
important result of tillage is that the soil is thoroughly
exposed to the influence of the air. Soils containing
humus or clay will absorb ammonia from the atmosphere,
and thus increase their store of nitrogen. The organic
remains of former crops and manuring are also oxidised,
the nitrogen being converted into nitric acid. The rocky
fragments which a soil contains, as fragments of silicates
or limestone, will at the same time be more or less dis-
integrated by the combined action of water and air, as-
sisted by the carbonic and humic acids arising from the
oxidation of vegetable matter, and a portion of the in-
soluble plant food be thus brought into a state suited for
assimilation by the roots of crops. In winter time the
disintegration of the various ingredients of the soil is
greatly assisted by frost. Water in freezing expands, and
thus rends asunder the substance frozen. Of the various
results brought about by tillage, the increased production
of nitrates must be ranked among the most important.

By drainage the various chemical actions we have just
mentioned are carried down to a greater or less extent
into the subsoil, for as the water level is lowered the air
enters from above to fill the cavities in the soil. By
drainage also the depth to which roots will penetrate is
increased, for roots will not grow in the absence of oxygen,
and rot as soon as they reach a permanent water level.
In a water-logged soil deoxidation is active, the nitrates
present are destroyed, a part of the nitrogen being evolved
as gas ; the soil may thus suffer a considerable loss of
plant food.

22 THE CHEMISTRY OF THE FARM.

Burning is occasionally resorted to as a means of in-
creasing the available plant food, and improving the
texture of a heavy soil. The soil is burnt in heaps, which
are then spread over the land. If the soil contains lime-
stone it is easy to see that the phosphates of the limestone
may become more available by the complete disintegration
which attends the conversion into lime. The lime will
also attack the silicates of the soil at a high temperature,
and liberate a part of the potash from its insoluble com-
binations. To produce the best results it is essential that
the burning should take place at a low temperature. This
treatment by burning is a very extreme one, and can be
recommended only in few cases ; it must always be at-
tended with an entire loss of the nitrogen in the soil burnt.
The ploughing in of burnt clay is of use in improving the
texture of heavy land.

CHAPTER III.

MANURES,

Diirerence between natural vegetation and agriculture — necessity for
manuring. Farmyard Manure. — Circumstances which influence its
character ; its average composition ;" slowness of its effect — Seaweed
similar to farmyard manure — Guano — Sulphate of Ammonium — Nitrate
of Sodium — Soot, Dried Blood, and Woollen Refuse — Bones — Ground
Phosphates — Su2)erphos]jhate — Gypsum — Lime, Chalk, and Marl —
Potassium Salts — Common Salt — Applicxttion of Manure — Importance
of thorougli distribution — Best time for application — The return
made by the crop.

In the natural vegetation of a forest or prairie the soil
suffers no diminution of plant food. The elements taken
from the soil are returned to it on the decay of the plants
which the soil has nourished, or on the death of the
animals which have fed on these plants. Under these
circumstances the surface soil becomes rich in carbon and
nitrogen, the quantity contributed by the atmosphere
exceeding all losses. The surface soil also becomes rich
in the ash constituents of plants, these being collected
from the subsoil by the roots, and left at the surface on
the decay of the plant. A virgin soil thus generally con-
tains an abundance of plant food, and will produce large
crops without manure.

In human agriculture, on the other hand, both vege-
table and animal produce are consumed off the land

24 THE CHEMISTRY OF THE FARM.

that has reared them. Provision must therefore be
made, sooner or later, to return to the land a part at
least of the plant food removed from it, if permanent
fertility is to be maintained. Hence the necessity for
manuring.

The most complete return to the land would be ac-
complished by manuring it with the excrements of the
men and animals consuming the crops. This is partially
done by the application of farmyard manure ; but the
congregation of men in cities, and the difficulty of employ-
ing sewage with profit, prevent this plan being thoroughly
carried out. The farmer is thus generally obliged to
purchase manures for the land in exchange for the crops
and stock sold off it.

On very poor soils it is necessary to make a very com-
plete return of all the elements of plant food removed by
the crops, but in most soils there is an abundance of some
one or more of these elements, and a partial manuring will
consequently suffice. With high farming the contribu-
tions to the soil may be in excess of the exports, and the
land consequently increase in fertility. The nature of the
exhaustion resulting from the growth of particular crops,
and the economic application of manure to meet their
special requirements, will be considered in Chapter IV.
The losses which a farm sustains by the sale of animal
products will be treated of in the section on " The Con-
stituents of Animals," page 61.

Farmyard Mannre consists of the liquid and solid
excrements of the farm stock, plus the straw employed as
litter. Its composition will vary according to the charac-
ter of the animals contributing to it, the quality of their

MANURES. 25

food, and the nature and proportion of the litter. The
composition of the manure will also depend a good deal
upon the method in which it has been prepared.

In the case of an adult animal, neither gaining nor
losino^ weiojht — a workino^ horse for instance — the excre-
ments will contain the same quantity of nitrogen and ash
constituents as was present in the food consumed. If
however the animal is increasing in size, is producing
young, or furnishing milk or wool, the nitrogen and ash
constituents in the excrements will be less than those con-
tained in the food, the difference appearing as animal
increase. The manure from animals of this class will
therefore be poorer than that obtained from the former
class, supposing the same food given to each. We must
not expect valuable manure from a cow in full milk, or
from a rapidly growing pig.

The character of the food will affect the quality of the
manure even more than the character of the animal. A
diet of maize and straw chaff can yield only a poor
manure, because these foods contain very little nitrogen
or phosphates. A diet including a liberal amount of oil-
cake or beans will, on the other hand, yield a valuable
manure, these foods being rich in nitrogen and ash consti-
tuents. A common mode of increasing the supply of
manure on a farm is by the consumption of purchased
food, by the stock. This part of the subject will be more
fully discussed in Chapter IX.

The treatment of the manure is also most important.
A large proportion of the nitrogen is voided in the form
of urine, and generally the richer the diet the higher will
this proportion be. If, therefore, the manure is washed by
rain, and the washings are allowed to drain away, serious

2G THE CHEMISTRY OF THE FABM.

loss -Nvill occur. Hence the superiority of box manure to
that made in an open yard.

It must also be recollected that the urea, which forms
the chief nitrogenous ingredient of urine, is speedily
changed by fermentation into carbonate of ammonium ;
as this is a volatile substance, a loss of a part of the
nitrogen may easily occur, especially if an insufficient
amount of litter is employed.

Farmyard manure rapidly undergoes fermentation. If
placed in a heap the mass gets sensibly hot, and a large
quantity of carbonic acid is given off. When the fer-
mentation occurs in a place protected from rain carbona-
ceous matter is destroyed, but little loss of nitrogen takes
place. Rotten manure, when well made, is more con-
centrated than the fresh, having diminished in weight
during fermentation, with but little loss of valuable con-
stituents. Some of the constituents have also become
more soluble.

Farmyard manure will contain from 65 to 80 per cent,
of water. The nitrogen may be 0.40 to 0.G5 per cent., or
higher, if produced by highly fed animals. The ash con-
stituents will be 2.0 to 3.0 per cent., exclusive of the sand
and earth always present. Of these ash constituents OA
to 0.7 will be potash; and 0.2 to 0.4 phosphoric acid. One
ton of farmyard manure will thus supply 9 — 15 lb. of
nitrogen, a similar amount of potash, and 4 — 91b. of
phosphoric acid.

Farmyard manure is a "general" manure; that is it
supplies all the essential elements of plant food. The
immediate return from an application of farmyard manure
is much less than from the same amount of plant food
applied in artificial manures. The effect of farmyard

MANURES. 27

manure is spread over a considerable number of years, its
nitrogen being chiefly present not as ammonia but in the
form of carbonaceous compounds, which decompose but
slowly in the soil.

Seaweed when fresh is, on the whole, similar in value
to farmyard manure. It becomes more valuable as it
loses water.

Guano. — This manure consists chiefly of the dried ex-
crements of sea fowl. When guano has been deposited in
the absence of rain it contains a large amount both of
nitrogenous matter and phosphates. If exposed to rain
the original nitrogenous matter is decomposed, and the
nitrogen volatilised in the form of carbonate of ammonium ;
the guano remaining is then almost purely phosphatic.
Ichaboe guano, for example, is a recent deposit, containing
about 12 per cent, of nitrogen, and 12 per cent, of phos-
phoric acid ; while Mejillones guano is a phosphatic guano,
containing 0.9 per cent, of nitrogen, and 32.5 per cent, of
phosphoric acid. From its great variation in composition
guano should always be purchased on analysis.

In a nitrogenous guano the nitrogen is chiefly present
as uric acid, and as ammonium salts. The strong smell of
a damp guano is due to carbonate of ammonium. The
phosphoric acid exists principally in the form of phosphate
of calcium, but in nitrogenous guanos a small part exists
as phosphate of ammonium, a salt readily soluble in water.
Guano which has not suffered by washing may contain 3 to
4 per cent, of potash.

Nitrogenous guano is a highly concentrated manure,
and may be employed with excellent effect for corn crops,
potatos, and roots. Phosphatic guanos may be employed

28 THE CHEMISTRY OF THE FARM.

for turnips, but such guanos are more usually converted
into superphosphate before they are applied to the land.

Sulphate of Ammonium. — This substance is prepared
from the ammoniacal products of gas works ; in its
crystallised form it is the most highly nitrogenous of all the
manures at a farmer's disposal, containing about 20 per
cent, of nitrogen.

It should be ascertained in every case that the manure
is free from sulphocyanate of ammonium, as this substance
is very injurious to plants. If sulphocyanates are present
a solution of the salt will become blood-red on the addition
of ferric chloride.

Sulphate of ammonium is a " special " manure, valuable
solely for its nitrogen. It is a powerful manure for corn
crops, for which it is best employed in conjunction with
superphosphate.

Nitrate of Sodium. — An enormous deposit of the crude
salt, containing much chloride of sodium, is found in Peru.
The nitrate sent to this country has been purified by
crystallisation; it will contain about 15.6 per cent, of
nitrogen. The most usual impurity is common salt.

This manure, like the preceding, is valuable solely for
its nitrogen. It is an excellent manure for all crops
requiring artificial supplies of nitrogen, especially corn
crops and mangels. For corn crops it is best employed
together with superphosphate. Nitrate of sodium should
not be mixed with a damp superphosphate, else nitric acid
may be lost. It is best to mix the two immediately
before use ; or the superphosphate may be sown with the
corn, and the nitrate applied afterwards as a top dressing.

MANURES. 29

Nitrate of sodium is especially suited for clay land. It is
quicker in its action than any other nitrogenous manure,
and is therefore the best manure to employ when a late
dressing has to be given.

Soot, Dried Blood, and Woollen Refuse are all purely
nitrogenous manures. Soot owes its value to the presence
of a small and variable quantity of ammonium salts.
Dried blood is an excellent manure, containing 10 to 13
per cent, of nitrogen. Shoddy, and other forms of wool
and hair are very variable in composition, owing to
admixture of dirt, grease, and other foreign matter ; the
nitrogen they contain will range from about 5 to 10 per
cent.

The nitrogen of blood, wool, and hair, is not in a form
suitable as plant food. Blood readily decomposes in the
soil, yielding ammonia and nitric acid. Wool and hair
decompose much more slowly, and their effect is spread
over many years.

Soot is generally employed as a top dressing for spring
corn. Dried blood is an excellent manure for wheat.
Wool and hair are chiefly used for hops.

Bones. — These are largely employed as manure; the
fat is usually first extracted by steaming. Commercial
bones contain about 3.6 per cent, of nitrogen, and 23 per
cent, of phosphoric acid, existing as phosphate of calcium.
Bones that have been boiled to extract the gelatin contain
much less nitrogen, but a larger proportion of phosphates.

Bones decompose but slowly in the soil, especially on
heavy land ; their effect is thus spread over several years.
The finer the bones have been ground the more immediate

30 THE CHEMISTRY OF THE FARM.

is their effect. Bones are usually employed for pasture,
and for turnips.

Ground Phosphates. — Some phosphates when finely
gi'ound may on certain soils be successfully employed as
manure without previous conversion into superphosphate.
The phosphates most suitable for this purpose are phos-
phatic guanos, bone-ash, and South Carolina phosphate.
The soils most suitable for such manures are those rich in
humus, and poor in carbonate of calcium ; these being the
conditions (presence of humic and free carbonic acid) most
favourable to the solution of phosphate of calcium. Pas-
ture soils are especially suitable for such treatment. The
solution of the ground phosphate may be facilitated by
forming it into a compost with farmyard manure before
its application, or by employing with it sulphate of
ammonium. The phosphate should be employed in very
fine powder.

Superphosphate. — An abundance of mineral phosphates
(phosphates of calcium) occur in nature ; many of these
are so little soluble that their effect as manui-e is but
small ; by treating them with sulphuric acid the sparingly
soluble tricalcic phosphate is converted into the readily
soluble monocalcic phosphate, sulphate of calcium being
at the same time produced. Superphosphate is thus a
mixture of monocalcic phosphate, and generally some free
phosphoric acid, with gypsum, and various impurities (as
sand and compounds of iron and aluminium), derived from
the original mineral. A supei*phosphate will always
contain more or less of undissolved phosphate; this
amount will be more considerable if the manure is badly

MANURES. 81

made, or if the original mineral contained much ferric
oxide or alumina.

The value of a superphosphate chiefly depends on the
percentage of " soluble phosphate" present. By this term
analysts do not mean monocalcic phosphate, but the quan-
tity of tricalcic phosphate rendered soluble.

The best mineral phosphate found in England is Cam-
bridge coprolite. This is largely used for making super-
phosphate. Other coprolites are also employed, but they
are less suitable. Immense quantities of mineral phos-
phates are imported, principally from South Carolina,
Spain, Bordeaux, and Canada, besides considerable quan-
tities of phosphatic guano.

The superphosphates richest in soluble phosphate (40
to 45 per cent.) are prepared from phosphatic guanos.
Bone ash, and some phosphorites, also yield high quality
manures. The great bulk of our superphosphates is at
present prepared from Carolina phosphate or coprolite ;
such manure will contain 23 to 27 per cent, of soluble
phosphate.

Superphosphates form the basis of almost all manufac-
tured manures. By using bones, or by adding shoddy or
crude ammonium salts, turnip manures are produced con-
taining a small amount of nitrogen. By mixing with the
superphosphate a larger amount of ammonium salts, or
nitrate of sodium, the articles sold as corn, grass, mangel,
and potato onanures are prepared. Superphosphate made
largely from bones is known as dissolved hones.

When superphosphate is applied to a soil containing
carbonate of calcium, the soluble phosphate is speedily
precipitated, but in a form easily taken up by the roots oi
plants. In most cases the phosphoric acid is finally con-

32 THE CHEMISTRY OF THE FARM.

verted into basic phosphate of iron, a substance attacked
with difficulty by plants.

Superphosphates are naturally more speedy in their
efifect than manures consisting of undissolved phosphate.
A small quantity of phosphoric acid applied as superphos-
phate will have as great an effect as a considerable quantity
applied as bones or gi-ound phosphate.

Superphosphate is chiefly employed for turnips, for
which it is invaluable ; it is also of considerable use for
com crops, especially barley. Its use tends to early
maturity in the crop.

Gypsum. — This manure is one of limited value. It is
composed of calcium and sulphuric acid, and is most suit-
able for crops, such as clover and turnips, which require a
considerable amount of sulphur. As superphosphate
always contains much gypsum, special applications of
gypsum will be unnecessary where superphosphate is
employed.

Lime, Chalk, and Marl are frequently manures of the
greatest importance. On soils naturally destitute of lime,
as is the case with many clays and sandstones, these
manures will supply an indispensable element of plant
food. Some marls will also supply a notable quantity of
phosphoric acid. In most cases, however, the beneficial
influence of these manures is due to the chemical actions
which lime performs in the soil ; the chief of these have
been already glanced at under the head of "Soil," (see
page 15).

Burnt lime is much more powerful in its action on vege-
table matter than chalk or marl ; it should be used with

MANURES. 33

discrimination, lest the humus of the soil be unduly dimin-
ished. Heavy clays, or soils rich in humus, are those most
benefited by burnt lime. In reclaiming peat bogs lime is
of the highest value. The acid humic matter of the peat
is neutralised by the lime, and the nitrogen held in com-
bination is converted into ammonia and nitric acid, and
thus made available to a crop.

The general effect of lime is to render available the
plant food already in the soil, without itself supplying
any significant amount ; liming cannot, therefore, be suc-
cessfully repeated except at considerable intervals.

Potassium Salts. — These salts are now obtained from
Stassfurt and Leopoldshall in large quantities ; they form
a thick deposit overlying an enormous mass of rock' salt.
The commonest potassium salt employed as manure is
kainit ; it consists of chloride of potassium, sulphate of
magnesium, and water, with frequently chloride of mag-
nesium and common salt in addition. Kainit will contain
13 to 14 per cent, of potash. Calcined kainit contains
less water, and some magnesia in place of the chloride of
magnesium; it will contain 15 to 17 per cent, of potash.

Wood ashes may also be employed as a potash manure ;
they will contain between 5 and 15 per cent, of potash.
The ash of young boughs is richer than that from full-
sized timber.

Potash manures produce their gi-eatest effect on pasture ;
clover and turnips may also be benefited by their use.
Many soils are naturally well furnished with potash, on
these soils potash manures are almost without effect.

Common Salt.— Chloride of sodium supplies no essential

34 THE CHEMISTRY OF THE FARM.

ingredient of plant food. The little value which salt pos-
sesses as a manure is probably due to its action in the soil,
where it may help to set free more important constituents.

Application of Manures. — A manure can be efficacious
only when its constituents are brought into contact with
the roots of the crop. To obtain this contact to the fullest
extent the manure must be thoroughly and evenly dis-
tributed throughout the depth of soil mainly occupied by
the roots. Soluble manures — as nitrate of sodium, chlo-
ride of sodium, ammonium salts, potassium salts, and
superphosphate — have the great advantage that they dis-
tribute themselves within the soil after the first heavy
shower far more perfectly than can be done by any mode
of sowing. TA^hen manure is especially required by the
plant in its earliest stages — as superphosphate for turnips
— it may be drilled with the seed ; but, as a rule, manure
should be sown broadcast, and ploughed in or harrowed.

Top-dressing, that is sowing manure on the surface of
land already under crop, should generally be confined to
manures that are soluble, or the principal constituents of
which easily become soluble in the soil. Nitrate of sodium
is sown with advantage in this manner if showery weather
can be depended on to distribute the manure in the soil.
On pasture all manures are necessarily applied as top-
dressings.

Whenever possible, manure should be reduced to a fine
powder before application. Artificial manures, if distri-
buted by hand, should first be made up to a considerable
bulk by mixing with fine dry soil or ashes. Manures con-
taining ammonia must not be mixed with alkaline ashes,
else some of the ammonia will be lost.

MANURES. 35

Manures of little solubility, or those for which the soil
has a great retentive power, may be applied to the land
some time before the growing period of the crop. Dif-
fusible manures, on the other hand, should be applied
only when the crop is ready to make use of them, else
serious loss may occur from drainage. Farmyard manure,
rape cake, and bones, and to some extent superphosphate
and potassium salts, belong to the former class ; while
nitrates, and all manures containing ammonia, belong to
the latter class. It was formerly supposed that the great
retentive power of fertile soils for ammonia would effectu-
ally prevent any loss by drainage ; we now know that
ammonia is speedily converted into nitrates after mixing
with the soil, and that these nitrates are readily washed
out by heavy rain.

Following these principles, an autumn manuring for
wheat may consist of farmyard manure, blood, or shoddy,
with or without superphosphate ; but dressings of guano,
ammonium salts, or nitrate of sodium should be deferred
till the spring. The question is, however, clearly one
of climate, and with a dry winter climate ammonium
salts or guano may be applied with advantage in the
autumn.

On soils of open texture, and little retentive power,
preference must often be given to manures of little solu-
bility, in order to diminish the loss occasioned by heavy
rain. Bulky organic manures, as farmyard manure or sea-
weed, are in such cases very suitable.

No dressing of manure is completely taken up by the
crop to which it is applied, dressings larger than the
actual requirements of the crop must therefore be applied
to obtain a given result. Soluble and active manures

D 2

oQ THE CHEMISTRY OF THE FARM.

produce their principal effect at once, and are of little
benefit to subsequent crops. Sparingly soluble manures,
and those which must suffer decomposition in the soil
before they are of service to the plant, as farmyard
manure and bones, will on the contrary continue to pro-
duce an effect over many years. Farmers have a preju-
dice in favour of the latter class of manures, but it is clear
that the quickest return for capital invested is afforded by
the former class.

Nitrogen applied as ammonium salts or nitrates will
give all its effect during the first year ; 45 to 50 per cent,
of the nitrogen applied in this form to wheat and barley is,
according to Lawes and Gilbert, recovered on an average
in the increase. In the case of farmyard manure, applied
on the heavy land at Bothamsted to wheat and barley,
only about 10 to 15 per cent, of the nitrogen was recovered
in the increase, but the effect on the barley continued
many years after the application of the manure ceased.
It is evident that a small quantity of an active manure
will accomplish the same work as a large quantity of one
less active.

The residues of phosphatic and potassic manures are
available for subsequent crops, but are distinctly less active
than fresh applications of the same manures.

CHAPTER IV.

CROPS.

The dry matter, nitrogen, and ash constituents, in average crops. Cereal
Ci'ops. — Characteristic composition — Mode of feeding — Most suitable
manuring. Mcadoio Hay. — Characteristic composition — Demand for
ash constituents — Influence of manures on quantity and quality —
Pasture especially suited for obtaining nitrogen from the atmosphere.
Leguminous Crops. — Characteristic composition — Source of nitrogen
obscure— Clover-sickness. Boot Crops. — Characteristic composition
— Differences in the nutrition of turnips, mangels, and potatos. Forest
Groicth. — Large production of dry matter for small consumption of
ash constituents and nitrogen. Adaptation of Manures to Crops. —
The feeding power of each crop must be taken into account — Economic
distribution of manure in a rotation — The practical value of manures
only known by experiments on each farm. Inflicencc of Climate and

To understand the chemistry of crops we must first
inquire as to their composition. The following table gives
the average composition of ordinary farm crops and of the
annual produce of three kinds of forest. The quantities
of carbon, hydrogen, and oxygen present are omitted, also
some of the smaller ash constituents. By "pure ash" is
understood the ash minus sand, charcoal, and carbonic
acid.

The composition of grain, and of all seeds, is tolerably
constant ; but the composition of straw, leaves, roots, and
tubers, will vaiy very considerably according to the
character of the soil, manure, and season.

38

THE CHEMISTRY OF THE FARM.

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40 THE CHEMISTRY OF THE FARM.

Cereal Crops. — These contain mucli less nitrogen than
either the leguminous or root crops ; about three-quarters
of the nitrogen is in the com, and only one quarter in the
straw. The amount of phosphoric acid is not very different
from that found in other crops ; this ingredient is, in fact,
the most constant of all the constituents of crops ; it is
chiefly concentrated in the corn. Potash and lime are
present in much smaller quantity than in other crops ;
they are chiefly concentrated in the straw.

The presence of a large amount of silica is characteristic
of the cereal crops ; they possess apparently a capacity for
feeding on silicates not enjoyed by other crops. The base
of the silicate is made use of by the plant, while the silica
itself is excreted upon the surface of the leaves and straw.
It has been shown that silica is by no means essential
for the growth of cereals; they take it up freely, but
can also do without it. *

The autumn sown cereals (wheat and rye) have both
deeper roots, and a longer period of growth, than the
spring sown cereals, and are better able than the latter
to supply themselves with the necessary ash constituents
from the soil. Barley possesses a considerable development
of root near the surface, and is apparently more capable
of obtaining nitrogen from the soil than wheat.

Cereal crops derive their nitrogen almost exclusively
from nitrates ; the form in which the great bulk of the
nitrogen is present in the soil is unsuitable for them.
Notwithstanding, therefore, the small amount of nitrogen
contained in cereal crops, they rank among those most
benefited by nitrogenous manures. Phosphates, though
of little use by themselves, are also beneficial (especially
in the case of spring crops) when applied with nitrogenous

CROPS. 41

manure. A nitrogenous guano, or an application of
nitrate of sodium and superphosphate, is generally the
most effective manuring for a cereal crop.

Meadow Hay. — The grasses which form the main bulk
of hay belong to the same family of plants as the cereal
crops ; the seed, however, in grass bears such a small pro-
portion to the stem and leaf that meadow hay may be
regarded as a straw crop. In accordance with this
character hay is found to contain a much larger propor-
tion of potash and lime than cereal crops, and a much
smaller amount of phosphoric acid.

The roots of grass being far shorter than those of the
cereals are less able to collect ash constituents from the
soil ; if therefore grass is mown for hay, manures contain-
ing potash, lime, and phosphoric acid will generally be
required. Like the cereal crops grass is greatly increased
in luxuriance by the application of soluble nitrogenous
manures.

Farmyard manure, or the feeding of cake, corn, or roots
on the land, is the most appropriate manuring for per-
manent pasture, if quality as well as quantity of produce
is considered. Large crops of hay may be obtained by
manuring with nitrate of sodium, together with kainit and
superphosphate, but a continuance of such treatment pro-
motes a coarse herbage.

The natural clovers of a meadow are destroyed by the
continued application of highly nitrogenous manures, a
hay consisting almost exclusively of grass being produced.
The clovers are developed by the application of manures
supplying potash and lime, and by pasturing instead of

42 THE CHEMISTRY OF THE FARM.

The perennial character of grass, and the abundance of
humus in a pasture soil, present favourable conditions for
the collection of nitrogen from the atmosphere ; this takes
place to a greater extent on pasture land than with most
other crops.

Leguminons Crops. — Some of these are grain crops, as
beans and peas; others are fodder crops, as red clover,
sainfoin and lucerne. A striking characteristic of all these
crops is the large amount of nitrogen which they contain,
the quantity being about twice as great as that found in
cereal crops. The quantity of potash and lime in le-
guminous crops is also very large. The relative proportion
of these two bases varies much in crops grown on different
soils ; upon a calcareous soil lime will preponderate in the
crop, but on a clay soil potash. The lime is found chiefly
in the leaf. Silica is nearly absent in leguminous crops.

The nutrition of leguminous crops is not at present
perfectly understood. A good crop of red clover, when
cut for hay, removes a large quantity of nitrogen from the
land, but it nevertheless leaves the surface soil actually
richer in nitrogen than it was before from the residue of
roots and stubble left in the soil. From whence is this
large quantity of nitrogen obtained ? It must be procured
either from the subsoil, or the atmosphere. The former
seems the more probable, as experiments have hitherto
failed to prove that leguminous plants have any special
power of obtaining nitrogen from the air. The question is
further complicated by the fact that nitrogenous manures
generally produce but little effect upon leguminous crops.
It seems pretty certain that leguminous crops possess to
some extent a distinct source of nitrogen ; they are pro-

CHOPS. 43

bably capable of feeding on some compounds of nitrogen
and carbon which are comparatively useless to other crops,
and hence the facility with which they acquire nitrogen
from the soil. A deeply rooted crop like red clover collects
nitrogenous compounds from the subsoil, and accumulates
nitrogen at the surface in the form of a crop.

The particular food supply of a leguminous crop be-
comes exhausted by repeated cropping, and the land is
said to be "clover" or "bean sick;" no means of
remedying this condition is known save by the growth of
other crops for a series of years.

Potash manures have generally a very beneficial effect
upon leguminous crops ; they fail, however, to cure clover
sickness. Gypsum is also valuable, though to a less
extent.

Root Crops. — All these crops contain a large amount
both of nitrogen and ash constituents ; among the latter
potash greatly preponderates. Turnips contain more
sulphur than any other farm crop.

The turnip and mangel crop differ in several respects.
Turnips and swedes draw their food chiefly from the sur-
face soil. Their power of taking up nitrogen from the soil
is distinctly greater than that of the cereal crops. Turnips
are also well able to supply themselves with potash when
growing in a fertile soil, but they have singularly little
powder of appropriating the combined phosphoric acid of
the soil; fresh applications of phosphatic manures thus
always produce a marked effect on this crop.

Mangels have far deeper roots than turnips, and also a
longer period of growth. They have a great capacity for
drawing food from the soil, including both nitrogen,

44 THE CHEMISTRY OF THE FARM.

potash, and phosphoric acid. When carted off the land
they are probably the most exhaustive crop that a farmer
can grow. As mangels have not the same difficulty that
turnips have of attacking the combined phosphoric acid of
the soil, phosphatic manures are, in their case, of much
less importance. Purely nitrogenous manures, as nitrate
of sodium, when applied alone to mangels, generally pro-
duce a great effect on the crop ; this is not the case with
turnips, which require phosphates as well as nitrogen in
their manure.

As both turnips and mangels consume extremely large
amounts of plant food, a liberal general manuring with
farmyard manure is in most cases essential for the pro-
duction of a full crop ; but the special characteristic of
the manure for turnips should be phosphatic, and of that
for mangels nitrogenous.

Potatos are surface feeders, and require a liberal general
manuring to ensure an abundant crop.

As both^root crops and potatos require large supplies
of potash, kainit will be found of service on land naturally
poor in that ingredient. It will be chiefly required when
the crops are raised with artificial manures only, as farm-
yard manure will always supply a considerable amount of
potash.

Forest Growth. — The figures given in the table repre-
sent the composition of the produce of beech, spruce
fir, and Scotch pine forests felled for timber, and are
the results of extensive investigations made in Ba-
varia. Nitrogen, sulphur, and chlorine determinations
are wanting.

The amount of dry matter in the annual forest growth

CROPS. 45

is in excess of that yielded by any of the cultivated crops
given in the table, excepting maogels. This large produce
is obtained by a very small consumption of soil food ; the
amounts of potash and phosphoric acid required are espe-
cially far less than in the case of any farm crop. The
greater part both of the ash constituents and nitrogen is
found in the fallen leaves ; if these are left undisturbed,
and allowed to manure the ground, the requirements of
the forest become extremely small. It appears that about
3000 lbs. of perfectly dry pine timber are produced with a
consumption of only 2J lbs. of potash, and 1 lb. of phos-
phoric acid per acre per annum ; with beech timber the
quantities required are rather larger. The nitrogen con-
tained in timber is very small in amount, but the actual
quantity required by a forest has not been accurately
ascertained. The growth of forest timber is plainly far
less exhaustive to the soil than ordinary farm culture.
The demand on the soil becomes, however, considerably
greater if the trees are cut when young, young timber and
small branches being far richer both in nitrogen and ash
constituents than the mature wood.

Adaptation of Manures to Crops. — The true economy
of manure can be understood only when we are acquainted
with the special characters of the crops we cultivate. The
composition of a crop is no sufficient guide to the character
of the manure appropriate to it, even when we possess in
addition the composition of the soil on which it is to be
grown. It is not only the materials required to form a
crop, but the power of the crop to assimilate these
materials which must form the basis of our judgment.
This fact has been much overlooked by many scientific

46 THE CHEMISTRY OF THE FARM.

writers, who have counselled farmers to manure their land
in every case with all the constituents required by the
crop, a proceeding both impracticable and unnecessary.
In the case of a barren sand it may indeed be requisite to
supply all the constituents of plant food before a crop can
be grown, but such a case is far from the circumstances of
ordinary agriculture.

When land is in a fertile condition the total amount of
plant food available for crops is very considerable, and
luxuriant growth may be obtained by supplementing the
stores of the soil with the few particular elements of food
which the crop it is wished to grow has most difficulty in
obtaining. Thus, in a large majority of cases, a dressing
of nitrate of sodium and superphosphate will ensure a full
crop of wheat, barley, or oats, and in many cases nitrate
of sodium alone will prove very effective. These cereal
crops generally find the supply of nitrates in the soil
insufficient for their full growth, and the supply of
phosphates more or less inadequate ; but in a majority of
cases they are well able to obtain a sufficient supply of
potash, and other essential elements of food. We are
thus able, by supplying one or two constituents of the
crop, to obtain a luxuriant harvest. In the same way
nitrate of sodium employed alone will, in most cases,
produce a large crop of mangels ; superphosphate alone, a
large crop of turnips ; while potassium salts alone may be
strikingly effective with pasture and clovers.

This special manuring for each crop is no strain on the
capabilities of the soil if a rotation of crops be followed.
If superphosphate is applied for the turnips, potash for
the seeds, and a nitrogenous manure for the cereal crops,
the more important elements of plant food contained in

CROPS. 47

the soil will not be diminished at the end of the rotation.
At the same time the most economic result will have been
obtained from the manures employed, for each manure
will have been supplied to that particular crop with which
it yields the most remunerative result.

It is doubtless possible by means of rotations manured
on the above principles to farm successfully with the sale
of all the crops produced, and without the use of farmyard
manure ; this is possible at least so long as artificial
manures can be obtained at a low price. In the majority
of cases, however, the special manuring will only be
required to supplement the general manuring by farm-
yard manure. Under these circumstances it would seem
best, from a chemical point of view, to apply the farmyard
manure to those crops which most require potash, or
which stand most in need of a general manuring ; such
crops would be pasture, seeds, turnips and potatos.

The economic value of potash manures varies much on
different soils. As potassium salts are an expensive
manure, the farmer should always ascertain by means of
small field experiments whether they will, in his case,
yield a remunerative result, before employing them on
any large scale.

As the whole object of artificial manuring is to supple-
ment the deficiencies of the soil, it is highly desirable
that a farmer should ascertain by trials in the field what
is the actual amount of increase which he obtains from
the application of the manures he purchases. A few care-
fully made experiments will teach him what his land and
crops are really in need of. Should he add superphosphate
with the nitrate of sodium for his wheat ? What dressing
of the nitrate is most economical ? Is superphosphate alone

'48 THE CHEMISTRY OF THE FARM.

sufificient for his turnip crop, or should guano or nitrate be
employed as well ? What is the smallest quantity of
superphosphate sufficient for the crop ? Will it pay to
use potassium salts for his seeds or pasture ? These and
many other questions can only be answered by trials on
his own fields, and on the farmer's knowledge of such facts
will depend the economy with which he is able to use
purchased manures.

Influence of Climate and Season. — The influence of
weather upon crops is far greater than the influence of
manure.

As a plant contains water as its largest constituent, and
as the whole of the plant food obtained from the soil is
taken up through the medium of water, while the amount
of water daily lost by the plant through evaporation is very
large, the necessity of a sufficient supply of water in the
soil during the growing period of a crop is very evident.
On the other hand, an excess of water in the soil prevents
root development, and causes a loss of nitrates and other
soluble plant foods in the drainage water. Deeply rooted
crops, as wheat, red clover, and mangel, are those best
fitted to resist drought ; while shallow-rooted crops, as
grass and turnips, are those which suffer most from it.

We have already seen that carbon, which forms the
largest ingredient of all vegetable substances, is obtained
by plants exclusively from the atmosphere under the in-
fluence of light, and that a certain temperature is necessary
for this assimilation of carbon, and for the other chemical
processes which proceed in a growing plant ; a sufficient
supply of light and heat is therefore plainly required
for the production of a crop. In a season of de-

CROPS. 49

ficient light and heat the harvest is always late, growth
having taken place more slowly than in an average
season. In the case of extremely cold and cloudy summers
the whole season may be too short for maturing the crop,
and the seed in consequence may never be fully ripened.

Each crop requires more or less a different climate for
its perfect development ; a knowledge of the kind of
climate best suited to each crop is of great service in
selecting crops for any particular district. Thus wheat
requires hot and dry weather for its ripening period, while
oats will ripen in a moist atmosphere. Mangels require
heat, and can resist drought, while turnips develope best
in a cool moist air. Oats and turnips thus best suit a
Scotch climate, while wheat and mangels are better
fitted for the south-east of England.

The soil best furnished with plant food is the one which
will yield the best results in adverse seasons, the crop
having a greater amount of vitality, and being able to
turn to the best advantage the short periods of favourable
weather that may occur. Poor soils yield their best results
in seasons of slow but continued growth, the crop having
a longer time to collect the scanty supply of food which
the soil contains. In hot seasons, with an early harvest,
only soils well supplied with food can produce full crops.

The character of the winter has often considerable in-
fluence on that of the following season. In a wet winter
the soil may lose nitrates by drainage to a considerable
extent. Koot development will also be prevented by ex-
cessive wet. After such a winter the wheat crop gene-
rally is in a backward condition, and finds itself in an
impoverished soil. The injurious effects of severe frost
are well known.

CHAPTER V.

ROTATION OF CROPS.

The aim of rotations — Results of bare fallow — Effect of green crops, fed on
the land or ploughed in — Distinctive characteristics of crops — Dif-
ferences in periods of growth, depth of roots, powers of assimilation,
and quantity of food demanded — Losses to the land during rotation —
Actual loss in an assumed four-course rotation — Probable gain of
nitrogen from the atmosphere — Sale of j)roduce other than corn and
meat.

It is by no means impossible to grow tlie same crop
"with success year after year on the same land ; ordinary
pasture is indeed an example of continuous cropping.
The Rothamsted experiments show that excellent crops of
wheat, barley, and mangel may be continuously obtained
if appropriate manure is annually applied, and the land
kept free from weeds. A rotation of crops is resorted to
in ordinary practice from the facilities which such a plan
affords for cleaning the land, and from the greater economy
of manure which results from this practice. One of the
principal aims of a rotation is to bring the land from time
to time into a condition suitable for growing cereal crops ;
this suitable condition consists mainly in the accumula-
tion of nitrogenous plant food in the surface soil.

Bare Fallow. — A bare fallow is one of the oldest modes
of preparing soil for wheat. The soil is ploughed, and
exposed a whole year to atmospheric influences, and

ROTATION OF CROPS. 51

finally sown with wheat. In the case of a clay soil, this
treatment would probably lead to the following results : —

1. An improvement in the mechanical texture of the soil.

2. The disintegration of some of the mineral silicates,
whereby potash and other necessary ash constituents of
plants would be liberated and made available for vegeta-
tion. 3. The absorption of ammonia from the atmosphere
by the soil. 4. The receipt of both ammonia and nitric
acid from the air in the form of rain. 5. The oxidation of
ammonia, and of the vegetable remains in the soil, nitric
acid being produced.

The production of nitric acid is probably the most
important result of a bare fallow. In soils at E-othamsted
left as bare fallow, there has been found at the end of
summer 34 — 55 lb. of nitrogen per acre in the form of
nitric acid in the first 20 inches from the surface. Sup-
posing the season of fallow is a fairly dry one, the increase
in the available nitrogenous food will probably enable the
soil to produce twice as much wheat as it could do without
this treatment. If, however, the soil is exposed to heavy
rain, the nitrates produced will be more or less washed
out, and the benefit of the fallow greatly diminished.
Bare fallow can be used systematically with advantage
only on clay soils having a considerable absorptive power
for ammonia, and in a tolerably dry climate ; under other
circumstances a continuance of the practice must issue in
a serious loss of soil nitrogen.

Green Crops. — The most usual plan for bringing land
into condition for the growth of cereals is the cultivation
of green crops. These may be ploughed in, forming what
is termed green manuring; or consumed on the land by

E 2

52 THE CHEMISTRY OF THE FARM.

the farm stock ; or the crop may be removed, consumed
in cattle-sheds or in the farmyard, and the resulting
manure brought on to the land. The principle in every
case is that the constituents of the crop shall be returned
to the soil.

Let us suppose that land is laid down with seeds, which
after two or three years are ploughed up, and a cereal
crop taken. While the land is continuously covered by
vegetation the loss of nitric acid by drainage will be
reduced to a minimum. If the grass is fed off on the
land, the surface soil will at the end of the three years be
considerably enriched both with ash constituents and
nitrogen. The former have been collected from the sub-
soil by the roots of the crop, and returned to the surface
as animal manure. The latter includes the accumulated
receipts from the atmosphere during the three years,
minus the quantity lost by drainage and that assimilated
by the animals. The accumulated nitrogen wdll be
chiefly in the form of gi'ass roots, stems, and humus.
When such land is ploughed up, the vegetable matter and
humus are oxidised, and gradually yield their nitrogen as
nitric acid.

Such a mode of cropping has an advantage over a bare
fallow in several ways: — 1. The land is turned to profit-
able use, food being produced for the farm stock. 2. Both
ash constituents and nitrates are collected from the sub-
soil, and brought to the surface. 3. The nitrogen is kept
in an insoluble form, as vegetable matter, and conse-
quently cannot be washed away, but accumulates to a
greater extent than in a bare fallow. 4. Humus is pro-
duced, the beneficial actions of which have already been
noticed. We have laid no stress on the enrichment of the

ROTATION OF CHOPS. . 53

land by means of ammonia taken up from the atmosphere
by the leaves of the crop, for nothing is known as to the
quantity of nitrogen which crops may thus acquire.

It follows from what we have just stated that the benefits
resulting from the growth of a green crop in a rotation
are greater in proportion as its period of growth is longer,
and its roots deeper. The more these conditions are
fulfilled the larger will be the accumulation at the surface
both of nitrogen and ash constituents, and the greater
consequently the increased fertility of the soil.

Leguminous crops, as already mentioned, have a special
power of accumulating nitrogen in the surface soil, and
are hence of the greatest value in a rotation. Red clover
is the most striking instance of this action. Its roots
extend further perhaps than those of any other farm crop,
and being biennial it has a long period for growth. The
accumulation of nitrogen at the surface in the form of
roots, stubble, and decayed vegetable matter, is in the case
of a good crop of clover so considerable, that the whole of
the above ground growth may be removed as hay, and the
land yet remain greatly enriched with nitrogen, and in an
excellent condition for producing a crop of wheat.

The ploughing in of green crops has some advantages
over the feeding of crops on the land. By this mode of
proceeding the whole of the crop is returned to the soil,
whereas in feeding a small part of the nitrogen and ash
constituents is retained by the animal. The characteristic
advantage of green manuring lies, however, in the large
amount of humus which the soil acquires. All the carbon
which the crop has obtained from the atmosphere is in
this case incorporated with the soil, instead of being con-
sumed by the animal. Green manuring is especially

54 THE CHEMISTRY OF THE FARM.

adapted for light sandy soils, which need humus to increase
their retentive power.

Having glanced at the general advantages to be derived
from alternating green crops with cereals, we will consider
next the characteristics of different crops which specially
fit them to succeed or prepare for each other.

Distinctive Characteristics of Crops. — Differences in
their periods of growth occasion a marked distinction in
the relation of different crops to soil nitrogen. Thus the
fact that the active growth of the cereals commences in
spring, and concludes at their time of blooming towards
the end of June, places these crops at a disadvantage
as to the supply of nitrates from the soil. The autumn
and winter rains have frequently washed out the greater
part of the nitrates contained in the soil before the
growth of the cereal crop commences, and nitrification in
the soil has not long recommenced its activity in summer
time when the crop becomes too mature to appropriate
fresh supplies of nitrogen. Continuous wheat cropping
thus results in a gradual impoverishment of soil nitrogen
by winter drainage, over and above the nitrogen actually
removed in the crops, and thus necessitates a considerable
application of nitrogenous manure if fertility is to be
maintained.

A root crop sown in early summer, on the other
hand, has at its disposal all the nitrates that would be
available for wheat or barley, and in addition the large
supply of nitrates formed in the soil during summer and
early autumn. A great part of the nitrates which would
be lost in cereal cultivation is thus assimilated and retained
by a root crop, and such crops are found to stand in less

EOTATION OF CROPS. 65

need of nitrogenous manure than cereals. By consuming
the roots on the land the nitrates collected by the crop
are returned to the soil in the form of animal manure,
and the land thus prepared to carry a cereal crop.
Similar remarks might be made respecting other green
crops whose active growth extends into tbe autumn.*

Another important dififereuce between crops lies in
their range of roots. Deeply rooted crops, as red clover,
sainfoin, rape, and mangel, and among the cereals wheat,
and rye, are to a considerable extent subsoil feeders, and
have a greater power of obtaining ash constituents from
the soil than shallow-rooted crops, as white clover,
potatos, turnips, and barley. In accordance with this
we find that superphosphate is a very effective manure
for the last three crops, but is much less required by such
crops as mangel or wheat. By growing deeply-rooted
crops as part of a rotation the subsoil is made to contri-
bute to the general fertility. Shallow-rooted crops, on
the other hand, have generally a special faculty for
appropriating food accumulated at the surface, and are
often of great use in this respect, as when barley is made
to follow turnips fed off on the land.

Yery little is definitely known as to the capacity of
different crops for assimilating different forms of plant
food, but there can be no doubt that this also is one of
the distinctions between various crops, and one reason of
the economy of a rotation. The most plainly marked
distinction as to mode of feeding is afforded by the be-
haviour of various crops towards silica. Graminaceous
crops, as the cereals and grasses, are apparently capable

* The writer is indebted to Mr. Lawes for the important ideas contained
in the two preceding paragraphs.

5G THE CHEMISTRY OF THE FARM.

of assimilating certain of the silicates contained in the
soil ; other crops exhibit no such capacity. In such a
case it is easy to imagine that an alternation of cereals
with crops of a different description may be for the benefit
of both, each drawing to some extent upon distinct sujj-
plies of food. Again, leguminous crops are clearly able
to assimilate nitrogen to a far greater extent than cereals,
and probably in some measure from a different source. If
crops of winter beans and winter wheat are grown on
similar unmanured land, the bean crop will generally
contain twice as much nitrogen as the wheat. The land
is not however impoverished for wheat by the growth of
beans, for wheat after beans will be a far better crop than
wheat after wheat, thus affording a striking example of
the advantages of rotation.

The quantities of plant food required by different crops
are given in the table printed on page 88 ; these also
furnish reasons for the alternation of crops. It will be
seen, for instance, that the cereals require but little potash
and lime, while root crops, beans, and clover, demand a
large supply ; it is obvious, therefore, that the resources
of the soil are husbanded by growing these two classes of
crops in alternation, the greater demand for potash and
lime thus falling every alternate year.

The nett result of a judicious alternation of crops, in
which the special characteristics of each are turned to
good account, is the production of a maximum total yield
of produce with a minimum amount of manure.

Losses to the Land dxiring Rotation. — The table show-
ing the composition of ordinary farm crops will supply the
requisite information as to the loss which a farm may

ROTATION OF CROPS.

67

suffer by the sale of individual crops. We will now con-
sider briefly the losses during a rotation.

The conservation of plant food on a farm is generally
effected by confining the exports to corn and meat, the
rest of the produce being consumed by the stock, and the
manure returned to the land. Let us assume that a farm
is managed on the four-course system, and that the
average crops obtained per acre are — swedes, 14 ton ;
barley, 40 bush.; seeds (half clover, half grass), 3 ton of
hay ; and wheat, 30 bush. Further, that nothing is sold
save corn and meat; that 2 bush, both of wheat and
barley are returned to the land as seed ; that 700 lb. of
linseed cake are fed with each acre of swedes ; that 110 lb.
of oats are purchased per acre per annum for the horses.
Finally, that half a ton of straw is fed per acre in the course
of the rotation, and the rest used as litter. Tltfi soiL will in
this case suffer the following losses of iHif^^ii) i)h^f?]^
acid, and potash, in the course of a ifiuL years' fl-^tafe«>n '

LOSSES PEK ACRE DURING A FOUa-XIC^^^E BOTATlWi.* * I

W

By feeding swedes, 14 ton . .

By sale ol barley, 38 bush.

By feeding seeds, 3 ton hay . .

By sale of wheat, 28 bush.

By feeding straw, i ton . . .

Nitrogen.

riiosphoric
acid.

J>.ota8fe-^

lbs.
11-1
32-3
18-7
30-8
0-7

lbs.

1-89
14-35

3-20
13-35

0-12

lbs.
0-24
9-60
0-40
9-05
0-02

Deduct manure from 440 lb. oats,
and 700 lb. oilcake .

93-6

36-8

32-91
14-61

19-31
12-02

Total loss in 4 years . . .

56-8

18-30

7-29

Average loss each year

14-2

4-57

1-82

58 THE CHEMISTRY OF THE FARM.

These losses assume that the farmyard manure is
properly made, and returned to the land without waste.
If the manure has suffered loss by drainage the estimates
given would have to be increased.

The loss of potash is extremely small, and may gene-
rally be quite disregarded. If, however, no cake is used,
and the land is poor in potash, the loss might be replaced
by the use of 1 cwt. of calcined kainit for the seeds.

The loss of phosphoric acid would be more than re-
placed, even if no cake were employed, by the use of 2
cwt. of superphosphate for the swedes.

The loss of nitrogen by the sale of crops and meat is
seen to be far more considerable than the loss of phos-
phoric acid or potash. The figures given are also below
the truth, as they do not take into account the nitrates
lost to the soil by drainage. Against this loss of nitrogen
we have to place the amount annually supplied to the
land by the rainfall, say 6 — 8 lb. per acre, and also the
unknown quantity absorbed as ammonia from the atmo-
sphere by soil and plant ; this latter amount will vary with
the nature of the soil and climate, and probably also with
the character of the cropping. We may, however, safely
assume that with the cropping and manuring supposed in
the preceding table the total gain of nitrogen from the
atmosphere will balance the loss, so that under good
management the rotation might be indefinitely continued
without diminishing the fertility of the land.

In the four-course manured rotation upon the heavy
land at Kothamsted, the nitrogen annually removed in the
crops, on an average of thirty-two years, has exceeded by
about 35 lb. the quantity supplied in the manure. If the
crops on this experimental rotation should be permanently

EOTATION OF CROPS. 59

maintained in quantity, of which at present we cannot be
certain, we must conclude that this 85 lb. of nitrogen,
together with the unknown additional quantity lost as
nitrate by drainage, have been annually derived from
the atmosphere — partly as rain, but mostly by direct
absorption b}^ soil or crop. It appears very probable
that on many soils the amount of nitrogen contributed
by the atmosphere in the course of a rotation is very
considerable.

We have supposed that only corn and meat are sold off
the land during the rotation ; it will often be economical
to sell a larger part of the produce, and to purchase
manure in its place. The sale of straw will be attended
with little practical loss on heavy land ; but on light land
both the loss of potash, and the diminution in the bulk of
the manure will be more or less felt. The sale of hay or
roots is far more exhaustive, and except on the most
fertile soils, must demand a considerable purchase of
manure or cattle food to replenish the soil with plant
nourishment.

CHAPTER VI.

ANIMAL NUTKITION.

The Constituents of the Animal Body. — "Water, albuminoids, gelatinoids,
horny matter, fat, and ash constituents — Composition of animals in
various stages of growth and fattening — Proportion of carcase — Com-
position of increase whilst fattening. ITic Processes of Nutrition. —
The constituents of food, and their particular functions in the body —
Digestion — Respiration — Excretion.

In order to understand the mode in which animals are
nourished we must first obtain some acquaintance with
the nature of the animal body, and understand the com-
position of the increase which takes place during growth
and fattening.

The Constituents of Animals. — The elements com-
posing the animal frame are the ten already named as
forming the essential constituents of plants (page 2),
with sodium and chlorine in addition. The two last
named elements are commonly present in the succulent
pai-ts of plants, but are apparently not essential to plant
life — in the animal frame they are, however, indispensable.
Pluorine and silicon are also always found in the animal
body, but are not known to be essential for life or growth ;
fluorine occurs in small quantities in the teeth and bones,
and silicon in hair, wool, and feathers.

ANIMAL NUTRITION. 61

The combustible matter of the animal body is mainly
composed of nitrogenous substances, and of fat.

The nitrogenous substances constituting the animal
frame may be generally classed as— (1) albuminoids ; (2)
gelatin oids ; and (3) horny matter. These three groups
are related in composition, though differing a good deal in
their properties. The albuminoids form the substance of
animal muscle and nerve, and the greater part of the solid
matter of blood ; they are, undoubtedly, of the first im-
portance in the animal economy. The gelatinoids form
the substance of skin and sinew, of all connective
tissue, and also the combustible matter of cartilage and
bone. Horny matter, named by chemists keratin, is the
material of which horn, hair, wool, and feathers are
constituted.

The fats occurring in the animal body are principally
stearin, palmitin, and olein. Stearin preponderates in
hard fats, and olein in fluid fats.

Of the incombustible constituents by far the largest
part is contained in the bones. In fat animals 75 to 85
per cent, of the total ash constituents are found in the
bones. Bone ash chiefly consists of phosphate of calcium,
with a small quantity of carbonate of calcium and phos-
phate of magnesium. In muscle by far the most abundant
ash constituent is phosphate of potassium. Potassium
salts are also abundant in the " yolk " of unwashed wool.
Blood, on the other hand, always contains a considerable
•quantity of sodium salts.

The amounts of water, nitrogenous matter, fat, and ash
constituents present in a large number of animals have
been determined at Eothamsted. The following table
shows the percentage composition of eight animals.

G2

THE CHEMISTliY OF THE FARM.

after deducting the contents of the stomachs and in-
testines : —

PERCENTAGE COMPOSITION OF WHOLE BODIES OP ANIMALS.

"Water .

Nitrogenous matter.
Fat ....
Ash

Fat
calf.

Half
fat
ox.

Fat
ox.

Store
sheep.

Fat
sheep.

Extra

fat
sheep.

Store
pig.

,Fat
pig.

65-1

15-7

15-3

3-9

56-0

18-1

20-8

5-1

48-4

15-4

32-0

4-2

61-0

15-8

19-9

3-3

46-1

13-0

37-9

3-0

37-1

11-5

48-3

3-1

58-1

14-5

24-6

2-8

43 0

11-4

43-9

17

The fat pig was one grown for fresh pork, not for bacon.

Water is in nearly every case the largest ingredient of
the animal body ; the proportion of water diminishes with
the gi'owth of the animal, and especially during fattening.
Fat forms in most cases the principal solid ingredient of
well fed animals, its proportion increases very largely
during fattening. The proportion of nitrogenous matter
and ash tends to increase from youth to maturity, but
diminishes during fattening.

The largest proportion of nitrogenous matter and of
ash are found in the ox, the smallest in the pig. The
difference in the proportion of ash is chiefly due to the
wide difference in the proportion of bone in these two
animals. Fat is found in greatest quantity in the pig, and
is least in the ox.

The following table shows the quantity of nitrogen, and
of the principal ash constituents, in the fasted live weight
of the fat animals analysed at E-othamsted. For conveni-
ence of comparison each animal is assumed to weigh
10001b. The table also gives the nitrogen and ash con-
stituents in wool and milk ; it thus supplies full informa-

ANIMAL NUTRITION.

63

tion as to the loss which a farm will sustain by the sale
of animal produce. The composition of wool is mainly
deduced from foreign analyses.

ASH CONSTITUENTS AND NITROGEN IN 1000 POUNDS OF
VARIOUS ANIMALS AND THEIR PRODUCTS.

Fat ox .
Fat sheep . .
Fat pig .
Wool, unwashed
Milk . . .

Nitrogen.

Phosphoric
acid.

Potash.

Lime.

Magnesia.

23-18
19-60
17-57
73-00
6-40

16-52

11-29

6-92

1-00

2-00

1-84
1-59
1-48
40-00
1-70

19-20

12-80

6-67

1-00

1-60

0-63
0-50
0-35
0-70
0-20

These figures show that the ox contains in proportion
to its weight a larger amount of nitrogen, and a much
larger amount of phosphoric acid and lime, than either
the sheep or pig. Of all the animals raised on a farm the
pig contains least of all the important ash constituents.

The large amount of potash in unwashed wool is very
remarkable ; a fleece must sometimes contain more potash
than the whole body of the shorn sheep.

In a fat ox about 60 per cent, of the fasted live w^eight
will be butchers' carcase; in a fat sheep about 58 per cent. ;
in a fat pig (fatted for pork) 83 per cent. The proportion
of carcase increases considerably during fattening. Thus
the carcase in the store sheep killed at Rothamsted
averaged 53'4, in the fat sheep 58*6, and in the very fat
sheep 64*1 per cent, of the fasted live weight.

When a lean animal is fattened the larger part of the
increase in live w^eight is carcase. It was found at
Kothamsted that in the case of sheep passing from the
"store" to the ''fat" condition, increasing in weight

(J4

THE CHEMISTRY OF THE FARM.

from 102 lb. to 155 lb., about 68 per cent, of the increase
was carcase. With "fat" sheep passing to the "very
fat" state, increasing from 144 lb. to 202 lb. live weight,
the proportion of carcase in the increase was about 77 per
cent. With a fattening pig, increasing from 103 lb. to
191 lb. live weight, the proportion of carcase in the
increase was found to be 91 per cent.

The percentage composition of the increase of sheep and
pigs when passing from the "store" to the "fat" con-
dition is about as follows. The increase of fattening oxen
will have a similar composition.

PERCENTAGE COMPOSITION OF THE INCREASE WHILST
FATTENING.

Sheep ....
Pigs ....

Water.

Nitrogenous
matter.

Fat.

Ash.

22-0
28-6

7-2
7-8

68-8
63-1

2-0
0-5

The increase during the fattening stage of growth is
thus chiefly an increase in fat, eight to nine parts of fat
being laid on for one of nitrogenous matter. The pro-
portion of fat would be somewhat greater still in the
increase of highly fattened animals, as, for instance, of
pigs fed for bacon.

The Processes of Nutrition. — We have already seen
that the food of plants is of the simplest character. From
such simple substances as carbonic acid, nitric acid, water,
and salts, a plant is able to construct a great variety of
elaborate compounds. It accomplishes these surprising
transformations by a consumption of force (sunlight)

ANIMAL NUTRITION. 65

external to itself. An animal has no such constructive
power. The animal frame is built up of substances ex-
isting ready formed in the food, or produced by the
splitting up or partial combustion of some of the food con-
stituents in the body. The animal also derives little or
no aid from external force. The temperature of the
animal (about 100° Fahr.) is maintained by the heat gene-
rated within the body from the combustion of the food
consumed ; the force by which all the mechanical work of
the animal is performed is also derived from the same
combustion of food. The source of force in the anim^
is thus purely internal.

It is evident from what has just been said that the food
of animals has duties to perform which are not demanded
of the food of plants. In plants the food merely provides
the matter for building up the vegetable tissues. In the
animal, besides constructing tissue, the food has to furnish
the means of producing heat and mechanical force.

1. Food Constituents and their Pnnctions. — The solid
ingredients of animal food may be classed generally as —
(1) albuminoids ; (2) fat ; (3) carbo-hydrates ; (4) incom-
bustible matter, or ash. Besides these general ingredients
of food we have in immature vegetable products a fifth
class — the amides, which also take part in animal nutri-
tion. The albuminoids and amides are nitrogenous
substances, the other ingredients of food are non-nitro-
genous.

The various albuminoids occurring in com, roots, and
other forms of vegetable food, are quite similar in com-
position to those found in milk, blood, and flesh. From
the albuminoids of the food are formed not only the al-

OG THE CHEMISTRY OF THE FARM.

buminoids of the animal frame, but also the gelatinoids,
the hair, wool, horn, &c., and to some extent the fat.
By the combustion of albuminoids in the body heat and
mechanical force will also be developed. Albuminoids
thus supply in themselves most of the requirements of the
animal — a statement which can be made of no other food
constituent. The albuminoids of food are frequently
described in analyses as " flesh-formers."

An animal, even when not increasing in weight, will
always require a certain constant supply of albuminoid in
its food to replace the waste of nitrogenous tissue which
is always going on ; the amount thus required is but
small, in the case of an adult man at rest it amounts to
about fifty grams (If oz.) per day.

When the nitrogenous tissues, or the albuminoids con-
sumed as food, are oxidised in the body, the nitrogen
they contkin is not burnt, but excreted in the form of
urea. The urea produced is one-third the weight of the
albumin oxidised. When the albuminoids, either of the
food or of the wasting tissues, are only partially oxidised,
fat as well as urea may be produced. Theoretically,
100 parts of albumin may yield 51 '4 parts of fat.

When amides are consumed as food they are burnt in
the system, and their nitrogen excreted as urea. Amides
cannot supply the place of albuminoids as muscle-formers,
but by combustion they serve for the production of heat
and force.

The fatty matter contained in food is similar to that
found in the animal body, but an animal is apparently
capable of transforming one kind of fat into another. The
fat of the food is either burnt in the animal system to
furnish heat and mechanical energy, or it is stored up as

ANIMAL NUTRITIOX. 67

a reserve of force. Fat has a greater value as a heat and
force producer than any other ingredient of food.

The carbo-hydrates of the food include starch, sugar,
and cellulose ; these substances consist of carbon, hydrogen,
and oxygen, the last two elements being in the proportion
to form water — hence the name. Various other non-nitro-
genous constituents of food, as pectin, lignose, and vege-
table acids, are also generally included under this title,
though not strictly speaking carbo-hydrates. Carbo-
hydrates form the largest part of all vegetable foods.
They are not permanently stored up in the animal body,
but serve, when burnt in the system, for the production of
heat and mechanical work. They are also capable, when
consumed in excess of immediate requirements, of con-
version into fat.

Carbo-hydrates are of less value, for the same w^eight
consumed, than either albuminoids or fat. Frankland
found that 100 parts of fat when burnt gave the same
amount of heat and force as 211 parts of albumin (urea
deducted), or 232 parts of starch. It is commonly reckoned
that 1 part of fat is equivalent to 2*44 parts of starch.
Cane sugar, according to the Rothamsted experiments with
pigs, has the same feeding value as starch. Celhdose,
being more difficult of digestion, has probably a smaller
value than either.

The amides, carbo-hydrates, and fat, are quite incapable
of adding to the nitrogenous tissues of the body. They
may, however, have this effect indirectly by protecting the
albuminoids of the food from oxidation. A moderate
quantity of albuminoids supplied to a growing animal will
thus produce a larger increase of muscle when accom-
panied by a supply of carbo-hydrates or fat than if con-

F 2

G8 THE CHEAIISTRY OF THE FARM.

sumed alone. In the foraier case the non-nitrogenous
ingredients of the food supply the heat and force de-
manded by the animal body, in the latter case the
albuminoids have to meet every requirement.

If an adult animal receives the small quantity of al-
buminoids and ash constituents necessary to supply the
waste of tissue, the whole of its remaining wants may
probably be met by supplies of carbo-hydrates and
of fat.

The ash constituents present in the food are the same
as those found in the animal body ; all that is accom-
plished by the animal is to select from the supply those
of which it is in want.

2. Digestion. — The object of digestion is to bring the
solid constituents of the food into a form suitable for ab-
sorption into the blood. Of the carbo-hydrates of the food
some, as sugar, are already soluble and diffusible, and need
no digestion ; others, as starch and cellulose, are naturally
insoluble. The digestion of carbo-hydrates commences
with the action of the saliva, which has the property of
converting starch into sugar. This action, in the case of
ruminants, is prolonged by the temporary sojourn of the
food in the first two stomachs, and its return to the mouth
in chewing the cud. The further solution of starch and
cellulose is effected in the intestines, partly by the pan-
creatic juice, which has a powerful action on starch, and
partly by the fermentive processes which take place.

The albuminoids of the food are attacked by the gastric
juice of the stomach (the fourth stomach of ruminants),
and converted into peptones, bodies similar to albuminoids
in composition, but which, unlike them, are diffusible

ANIMAL NUTRITION. 69

through a membrane. The pancreatic juice of the small
intestines also converts albuminoids into peptones.

Fat, liquefied by the heat of the body, is probably
capable of absorption without change. The digestion of
fat in large quantities is greatly assisted by the bile and
pancreatic juice.

The absorption of the dissolved constituents of the food
takes place more or less in all parts of the alimentary
oanal, but chiefly in the small intestines. The absorbed
matters pass into the blood.

The blood of an animal is the source of nourishment to
the whole body ; out of its ingredients all the tissues are
formed. The blood is also the means of conveying the
oxygen to the tissues which is essential to their vitality,
and of removing from them carbonic acid, and the other
products of their metamorphosis.

.3. Respiration. — The blood is supplied with oxygen
during its passage through the lungs, where it is brought
into contact with air. The oxygen is absorbed by the
hoemoglobin, which forms the chief constituent of the red
blood corpuscles. The scarlet blood thus produced is
■circulated through the whole body by the arteries; the
oxygen it supplies is consumed in the tissues, producing,
.among other results, heat and mechanical work. The
blood finally returns from the tissues by the veins. The
hoemoglobin has then lost its oxygen, and has assumed a
purple colour ; the blood serum also contains carbonic
acid gas in solution, and many other products of decom-
position. By passing again through the lungs the carbonic
.acid is more or less completely discharged, and a fresh
rsupply of oxygen obtained.

70 THE CHEMISTRY OF THE FARM.

4. Excretion. — The products which result from the
oxidation of tissue, or of the food consumed, are removed
from the body by the lungs, the kidneys, or the skin.
The chief products of oxidation in the body are carbonic
acid, water, urea, and salts. Carbonic acid is removed
through the lungs, and to a smaller extent by the skin •
urea and salts by the kidneys ; water by all the organs of
excretion.

Non-nitrogenous substances, as fat and sugar, when
oxidised in the body, yield .simply water and carbonic acid.
The nitrogen of the albuminoids, gelatinoids, and amides
is not oxidised, but is excreted in the fomi of urea. The
sulphur of the albuminoids is apparently oxidised to sul-
phuric acid.

The quantity of nitrogen in the urine is a measure of
the albuminoids, gelatinoids, and amides oxidised in the
body. In the urine are also removed all the salts not
required for the animal economy ; sodium and potassium
salts are generally abundantly present.

The solid excrement contains the undigested parts of
the food, with the residues of the bile, and other secretions
of the alimentary canal.

CHAPTER VII.

FOODS.

The Composition of Foods. — Detailed composition — Proportion of nitrogen
existing as true albuminoids — Variation in foods due to age and
manuring — Proportion between nitrogenous and non-nitrogenous
constituents — Ash constituents. Digestibility of Foods. — Method of
determination — Experiments with ruminants — Influence of age of
animal, daily ration, and labour — Influence of the maturity of fodder
crops on their digestibility — Influence of one food on the digestibility
of another — Common salt — Experiments with horses — Experiments
with pigs — Experiments with geese. Comjyarative Nutritive Value
of Foods. — Influence of proportion of water — Comparative heat and
work producing power— Proportion of albuminoids to non-albuminoids
— General conclusions.

In the preceding chapter we have enumerated the chief
constituents of food, and described their functions in the
animal body ; we may now proceed a step further, and
consider the detailed composition and feeding value of
the foods actually employed on the farm.

The nourishing value of a food is plainly fixed by two
factors : — 1. Its composition. 2. Its digestibility. The
first of these determines the character of the food — its
richness in albuminoids, fat, carbo-hydrates, and ash con-
stituents. The second determines the extent to which these
various constituents are made use of in the animal body.

Composition of Foods. — The average percentage com-
position of the foods commonly given to farm animals is

72

THE CHEMISTRY OF THE FARM.

shown in the following table. The figures given axe in
every case the mean of a large number of analyses.

PERCENTAGE COMPOSITION OF ORDINARY FOODS.

Food.

1

i

III

<

Cotton cake (decorticated)
Cotton cake (undecoili-

cated)
Linseed cake . . .

10-0

11-5
12-0

41-2^

24-6
28-1

14-0

6-2
12-0

18-0

30-2
30-3

9-0

20-8
11-0

7-8

6-7
6-Q

Beans ....
Peas

14-5
14-3

25-5

22-4

1-6
2-0

45-9
62-5

9-4
6-4

3 1
2-4

Oats ....
Wheat ....
Barley ....
Maize

13-0
14-4
14-0
11-4

12-9
11-3
10-6
10-4

6-0
1-5
2*0
5-1

53-8
68-1
63-7
68-5

10-8
30
7-1
3-0

3-5
1-7
2-6
1-6

Malt dust

Wheat bran . . .

Brewer's grains

9-5
14-0

77-4

23-7

14-2

4-8

2-2
4-2
1-4

44-9

50-4

9-7

12-5

11-1

5-3

6-8
6-1
1-5

Clover hay . ...
Meadow hay .

16-0
14-3

12-3
9-7

2-2
2-5

38-2
41-0

26-0
26-3

5-3
6-2

Bean straw . . . .
Wheat straw .

16-0
14-3

6-3

3-0

1-0
1-5

36-7
32-6

35-0
44-0

5-0
4-6

Meadow gi-ass . . .
Green clover .

80-0
83-0

3-5
3-3

0-8
0-7

19-2
7-0

4-5

4-5

2-0
1-5

Potatos ....
Mangels ....
Swedes ....
Turnips ....

75-0
88-5
89-3
91-7

21
1-2
1-5
1-1

0-3
0-1
0-2
0-2

20-5
8-2
7-3
5-3

1-1
1-0
1-1
1-0

1-0
1-0
0-6
0-7

The soluble carbo-hydrates in the above table include
stare h, pectin, and the finer parts of the fibre ; these are
not soluble in water, but are dissolved by the weak acid and
alkali employed by the analyst to separate the coarse fibre.

FOODS. 73

The whole of the nitrogen present in the foods above
mentioned has been reckoned as existing as albuminoids.
We are obliged to adopt this usual mode of calculation for
the sake of uniformity, the amoimt of true albuminoids
having been determined only in the case of a few of the
foods enumerated.

It has been shown during the last few years that a part
of the nitrogen in many foods exists, not as albuminoids,
but as amides {e.g., asparagine and glatamine) and as
nitrates. The subject is at present receiving the atten-
tion of chemists. It appears that in seeds nearly the
whole of the nitrogen exists as albuminoids, and this is
especially true of the kernel of the seed. Thus in wheat
flour about 90 per cent, of the nitrogen present is in the
form of albuminoids, while in the bran which forms the
skin of the grain only about 70 per cent, of the nitrogen
is in this condition. For the various cakes and grains
mentioned in the table the ficrures 2:iven for albuminoids
will be approximately correct, but for the other foods the
figures are undoubtedly too high. In hay it would appear,
from the few determinations made, that about 80 per
cent, of the nitrogen is present as albuminoids. In malt-
dust about 73 per cent of the nitrogen is albuminoid. In
potatos about 60 per cent, of the nitrogen is in this condi-
tion. The few determinations made in swedes show about
45 per cent, of the nitrogen as albuminoids. While in
mangels generally only about 25 per cent, of the nitrogen
is in this form.

The composition of all vegetable foods is liable to
variation, depending on the state of maturity of the
plant, and the character of the soil and season. In the
case of perfectly matured produce, as, for instance, ripe

74

THE CHEMISTRY OF THE FARM.

seed, the variations in composition are not generally con-
siderable, and an average composition, such as is given in
the table, will be found in most cases pretty correct. But
in the case of immature produce, such as meadow grass,
turnips, or mangels, the composition largely depends on
the stage of growth in which the plant is taken, and is
also greatly affected by the character of the manuring. It
may be generally stated that as a plant matures the pro-
portion of water, nitrogenous matter, and ash constituents
diminishes, while the proportion of carbo-hydrates largely
increases. At the same time the amides become more or
less converted into albuminoids.

The following table shows the percentage composition of
meadow grass cut at three different dates in the same field.
The first cutting will represent pasture grass fed off in the
green state by stock ; the second cutting is good ordinary
hay; the third cutting is an over-ripe hay, somewhat
coarse and stemmy, but well harvested. The composition
given in every case is that of the dry substance : —

COMPOSITION OF HAY HARVESTED AT DIFFERENT DATES.

Date of cutting.

Albumi-
noids.

Fat.

Soluble
carbo-hydrates.

Fibre.

Ash.

May 14 .
June 9. . .
June 26 .

17-65
11-16

8-46

3-19
2-74
2-71

40-86
43-27
43-34

22-97
34-88
38-15

15-33
7-95
7-34

Young grass is thus much richer in albuminoids,* and

* It must be bome in mind that in the present transition state of our
analyses of food, the tenn "albuminoids" will generally include all the
nitrogenous substances present.

FOODS. 75

contains a smaller proportion of indigestible fibre than
older grass, and is consequently more nourishing. The
same comparison may be made between young clover and
that which is allowed to mature for hay. Hay should
always be cut immediately full bloom is reached ; after
this point the quality of the crop will considerably de-
teriorate.

While fodder crops deteriorate towards maturity, from
the conversion of soluble carbo-hydrates into fibre, crops
such as potatos and mangel improve, the carbo-hydrates-
produced in their case being respectively starch and sugar,.
both of them substances of great feeding value.

The influence of high manuring is naturally to increase
the luxuriance of a crop; a luxuriant crop will always
contain more water than one in less active growth. Very
large mangels often contain only 6 per cent, of dry matter,,
while in quite small roots the proportion may be as high
as 15 per cent. Luxuriance also retards maturity. A
heavily manured mangel will contain, at the same date,
a much smaller proportion of sugar than a similar mangel
grown on poor soil. The result of high manuring is tlius
not only to increase the bulk of the crop, but also generally
to diminish the proportion of carbo-hydrates, and increase
the nitrogen, ash constituents, and water. In highly
manured crops a smaller proportion of the nitrogen will
exist as albuminoids than in crops less heavily manured
and more mature.

In the case of hay the composition is further affected by
the conditions of harvesting. Grass that has suffered from
rain during haymaking will contain less soluble matter
(carbo-hydrates and albuminoids) than well made hay^
this loss will be greatly increased if the hay has been

76 THE CHEMISTRY OF THE FARM.

long in the field, and undergone fermentation as well as

washing.

• Having pointed out the variations which are liable to

occur, we may now consider the average composition of

the -various foods shown in the table.

The amount of total dry matter is seen to be tolerably
uniform throughout the various classes of dry foods, the
foods richest in fat being generally the driest. In the
green fodder and roots the proportion of water is generally
very large ; potatos contain the most, and white turnips
the least proportion of dry matter.

We have already seen that albuminoids and fat are the
most concentrated forms of food which an animal can
consume ; those foods which are rich in albuminoids and
fat are therefore those which, generally speaking, have the
highest nourishing value. At the head of all foods in this
respect stand the various descriptions of oilcake ; they are,
without doubt, among the most concentrated foods at the
farmer's disposal. The leguminous seeds, as beans, peas,
and lentils, are rich in albuminoids, but not in fat. The
cereal grains are much poorer in albuminoids, containing
only about one-half the proportion found in leguminous
iseeds. Of the common cereals, oats are generally the
most nitrogenous, and maize the least. Oats and maize
are characterised by containing more fat than the other
cereal grains. The special characteristic of all the cereal
grains is their richness in an easily digested carbo-hydrate,
starch.

Of the three cereal products mentioned in the table
the bran and brewer's grains represent respectively the
husk of wheat and barley. These foods are richer both in
nitrogenous matter and fat, but contain a much more

FOODS. 77

considerable proportion of fibre than the whole grain.
Malt-dust (known also as malt-combs) consists of the
radicles of the germinated barley,which are removed afte .
the malt has been dried. This material is very rich in
nitrogenous matter.

When we turn to the hay, straw, green fodder, and
roots, the general composition becomes a less safe guide
to the nourishing value. The nitrogen, we have already
seen, is here no certain measure of the proportion of
albuminoids present. The fat credited to these foods is
also largely composed of waxy matters, and we can hardly
attribute to it the same feeding value as to an equal
amount of fat in oilcake or maize. The carbo-hydrates
also include various substances of little or no feeding
value. The same weight of dry matter in crude foods of
this class has thus a decidedly less nourishing value than
in foods consisting entirely of matured grain. Foods
belonging to different classes cannot safely be compared
on the basis of their composition.

An important element in the character of a food is the
proportion between its nitrogenous and non-nitrogenous
constituents, these two classes of ingredients performing
to a considerable extent distinct functions in the body.
To find this proportion it is usual to calculate the fat into
its equivalent in starch (generally done by multiplying
the fat by 2.44), and add the product to the other carbo-
hydrates of the food ; the relation of the albuminoids to
the total non-nitrogenous constituents reckoned as carbo-
hydrates is then easily found. The relation in question
is commonly known as the "nutritive relation" of the
food (Nahrstoffverhaltniss), but is better described as
the "albuminoid ratio." Thus the composition of wheat

78 THE CHEMISTRY OF THE FARM.

grain in the table shows an " albuminoid ratio " of 1 : 6.6,
and the composition of decorticated cotton cake an
albuminoid ratio of 1 : 1.5. Figures so calculated are,
however, only approximate, as we ought clearly only to
take account of the constituents actually digested by the
animal. We shall therefore refer to the subject again
further on.

Most foods supply a sufficient quantity of the ash con-
stituents which are required for the formation of bone
and tissue ; the chief of these are phosphoric acid, lime,
and potash.

The oilcakes and bran are the foods richest in phos-
phoric acid ; straw and meadow hay are the foods poorest
in this constituent. Lime is most abundant in clover
hay, bean straw, and turnips, and occurs in least quantity
in the cereal grains and in potatos. Potash is abundant in
roots, hay, bean straw, bran, and oilcake, and is found in
smallest quantity in the cereal grains.

Of all the ash constituents lime and soda are probably
the most generally deficient. Maize is of all ordinary
foods (rice excepted) the poorest in lime; it certainly
contains too small an amount for a rapidly growing
animal. At Rothamsted a mixture of coal ashes, common
salt, and superphosphate was used with advantage in the
case of pigs fed solely on maize. It must be recollected,
however, that animals will generally receive no incon-
siderable amounts of lime in their drinking water.

The proportion of phosphoric acid and potash in various
foods is shown in the table on page 114.

Digestibility of Foods. — Our knowledge concerning
the digestion of food by farm animals is almost entirely

FOODS. 79

derived from German investigations ; * mucli information
has already been obtained upon this subject, though a
great deal yet remains to be accomplished. The general
method of investigation has been to supply an animal
with weighed quantities of food, the composition of which
has been ascertained by chemical analysis. During this
experimental diet the solid excrements are collected and
weighed, and are finally analysed by the same chemical
methods previously applied to the food. Subject, there-
fore, to certain small corrections for intestinal secretions,
we obtain by this plan the amount of each constituent of
the food which has passed through the animal unabsorbed,
and by difference the amount digested. The proportion
of each constituent digested for 100 supplied as food is
known as its " digestion coefficient."

1. Experiments with Ruminants. — Ruminating animals
possess an extensive digesting apparatus, consisting of
the well-known four stomachs, in addition to the intestinal
organs. Food takes a considerable time in passing
through this system. In changing the diet of an ox five
days will generally elapse before the remains of the
preceding diet are expelled by the animal. Animals of
this class are specially adapted for the digestion of bulky
foods, containing much fibre.

Experiments have been made with oxen, cows, sheep, and
goats. The power of these different animals for digesting
food is apparently very similar, but no accurate compari-
sons have as yet been made. The following table shows

* The information given in this section is taken almost entirely from the
admirable work of Dr. E. Wolff, "Die Ernahrung der Landwirthschaftlichen
Nixtzthiere," with its valuable Supplement just published.

80

THE CHEMISTRY OF THE FARM.

the average results obtained with ruminating animals fed
on the foods respectively mentioned. The figures given
represent the " digestion coefficients " found for each con-
stituent of the food consumed. The " albuminoid ratio "
of the digested portion of the food is also given : —

EXPERIMENTS "WITH CATTLE, SHEEP, AND GOATS.

Food.

Digested for 100 of each constituent
supplied.

■3.

Ill

II

*3

ill

1

II

<

Linseed cake

Beans ....

Oats ....
* Barley ....
*Maize
♦Wheat bran . . .

Meadow hay

Clover hay . . .

Lucerne hay

Oat straw . . .
♦Wheat straw .
♦Bean straw . . .

80
90
71
81

88
67

59
59
59
51
46
50

84
88
79
77
79
75

56
55
76
38
20
51

90
93

84

100

85

50

47
56
38
30
36
65

78
93
76
87
91
70

62
69
67
43
39
60

?
?

24

?

?
37

57
44
40
61
56
36

1-7
2-1
6-5
8-2
7-9
4-5

9-2
6-2

2-8
14-7
4'4-l

6-2

"Roots and potatos are not mentioned in the table ;
they are apparently completely digested, with the excep-
tion perhaps of the small amount of hard fibre contained
in the epidermis and rootlets.

The digestibility of the foods in the lower division of
the table has been for the most part determined by

* These results are derived from one or two experiments only.
+ The numbers in this column refer to the foods actually used in the ex-
periments.

FOODS. 81

feeding the animals on these foods alone ; the digestibility
of the foods in the upper division has been found by
supplying them in various proportions along with hay, the
digestibility of which had been already ascertained with
the same animal. The amount of fibre in these last-
named foods is usually too small for its digestibility to be
determined with certainty by a few experiments.

The concentrated foods placed in the upper part of the
table are seen to be far more thoroughly digested than
is the case with hay or straw. When of good quality,
80 or 90 per cent, of the organic matter of these foods
will be assimilated by the animal, except in those cases
where much fibre is present. The albuminoids and fat
in these foods have especially a greater digestibility than
the same ingredients in hay and straw. The hard fibre
forming the husk of seeds is apparently but little diges-
tible. The oats employed were of somewhat inferior
quality.

In the case of ordinary hay and straw the organic
matter digested is but 45 to 60 per cent, of that supplied.
The minimum amount digested occurs with wheat straw ;
oat straw, which is generally cut somewhat more green, is
distinctly more digestible. The results given for meadow
and clover hay relate to hay of average quality; the
lucerne hay was of better quality, and shows a much
higher degree of digestibility in the nitrogenous matter.

The higher is the proportion of nitrogenous matter in
hay and straw, the greater appears to be its digestiblity.
Thus the wheat straw experimented with contained 4.8
per cent, of nitrogenous matter in its dry substance, of
which only one-fifth, or 20 per cent, v/as digested ; while
good lucerne hay with 19.3 per cent, of nitrogenous

82 THE CHEMISTRY OF THE FARM.

matter, had 76 per cent, of this in a digestible form. The
precise nature of the digested and undigested nitrogenous
matter has not yet been ascertained ; amides being sokible
bodies have probably been classed in these experiments
as digestible albumin.

Of the fibre in hay and straw about 40 to GO per cent.
is generally digested by ruminant animals. The fibre of
leguminous hay and straw (clover and lucerne hay, and
bean straw) is considerably less digestible than the fibre
of similar graminaceous foods (grass hay, oat and wheat
straw). It has been shown that both in the case of
the soluble carbo-hydrates, and of the fibre, the portion
digested has always the general formula of starch oi
oellulose, CgHjoOj, while the portion left undigested is
much richer in carbon. It appears, therefore, that while
oellulose is a digestible substance, the lignose which is
deposited in the tissues as the plant increases in age, and
which contains a larger proportion of carbon, is indigestible
Chemical analysis shows that the fibre of leguminous hay
and straw is richer in carbon, and consequently in lignose,
than the fibre of grass hay, or corn straw.

We must now glance at the circumstances which
influence the proportion of food digested. The individual
character of the animal undoubtedly affects the proportion
digested. Of two animals supplied with the same food,
one will often persistently digest a larger proportion than
the other. In young animals the digestive power is appa-
rently very similar to that of animals of full age. Sheep
from six to fourteen months old showed no distinct change
in digestive capacity.

Differences in the quantity of the daily ration of hay do
not sensibly affect the proportion digested ; an animal will

FOODS.

83

not digest more by being starved. Labour also is practi-
cally without influence, horses at rest and at work digesting
nearly the same proportion of their food. Differences in
the quality of a food may, however, exercise a great
influence on its digestibility ; the addition of another food
may also considerably alter the rate of digestion of the
first food.

The digestibility of fodder plants is mainly determined
by their age ; all the constituents of a young plant are
more digestible than in the same plant of greater age.
The composition of meadow grass cut at three different
dates has been already given on page 74 :- this grass was
supplied to sheep in the form of hay, and yielded the
following digestion coefficients : —

DIGESTION OF HAY BY SHEEP.

Date of cutting.

Troportiou of each constituent digested for
100 supplied.

Total
organic
matter.

Albumi-
noids.

Fat.

Soluble
carbo-
hydrates.

Fibre.

May 14 . . .

June 9 . . .

„ 26 . . .

75-8
64-3
57-5

73-3
72-1
55-5

65-4
51-6
43-3

75-7
61-9
55-7

70 -5
65-7
61-1

The diminution in digestibility with the increasing
maturity of the grass is very striking, and is very equally
spread over all the constituents. Similar experiments
with clover cut at different stages of growth have yielded
similar results. It follows plainly from what has been now
stated that no fixed nutritive value can be applied to
fodder crops, or to the hay made from them, as both their

84 THE CHEMISTRY OF THE FARM.

composition and digestibility are largely influenced by
their age and condition when cut. The young plant is
always the most nutritive.

The superior fattening quality of a pasture, as compared
with that of the hay made from it, is clearly due to the
fact that on land continuously grazed the animal is entirely
fed on young herbage, while hay will always consist of the
fully grown plant.

Fodder crops do not sensibly diminish in digestibility
by being made into hay, if haymaking is carefully carried
out in good weather. But the loss of the finer parts of
the plant by rough treatment, or the washing out of
soluble matter by rain, may considerably diminish the
digestibility. Hay appears to lose some of its digestibility
by keeping.

We now turn the influence of one food on the dis^esti-
bility of another.

If to a diet of hay and straw, consumed by a ruminant
animal, a pure albuminoid, as wheat gluten, be added, the
added food is entirely digested without the rate of diges-
tion of the original food being sensibly altered. The same
result has been obtained in experiments with pigs. These
animals were fed on potatos, to which variable quantities
of meat flour were afterwards added. The albuminoids of
the meat were entirely digested, while the proportion of
the potatos digested remained unchanged.

An addition of oil (olive, poppy, and rape oil) to a diet
of hay and straw is also apparently without unfavourable
influence on the rate of digestion ; indeed some experi-
ments with small quantities of oil (J lb. of oil per day per
1000 lb. live weight) show an improved digestion of the
dry fodder. With large additions of oil the appetite of

FOODS. 85

the animal for hay and straw is much diminished. Oil
supplied in moderate quantities is itself entirely digested.

An addition of starch or sugar to a diet of hay or straw,
diminishes its digestibility, if the amount added exceeds
10 per cent, of the dry fodder. The albuminoids of the food
suffer the greatest loss of digestibility under these circum-
stances ; the fibre also suffers in digestibility if the amount
of carbo-hydrate added is considerable. When starch has
been added, it is itself completely digested if the al-
buminoid ratio of the whole food is not less than 1 : 8.*

These facts are of considerable practical importance.
Nitrogenous foods, as oilcake and bean meal, may be given
with hay and straw chaff without affecting their digesti-
bility ; but foods rich in carbo-hydrates, as potatos and
mangels, cannot be given in greater proportion than 15
per cent, of the fodder (both reckoned as dry food) with-
out more or less diminishing the digestibility of the latter.
This decrease in digestibility may, however, be counter-
acted in great measure by supplying with the potatos or
mangels some nitrogenous food. When this is done the
proportion of roots or potatos may be double that just
mentioned without a serious loss of digestibility. Potatos
•exercise a greater depressing effect on the digestibility of
hay than roots, starch being more potent in this respect
than sugar. The cereal grains are rich in starch, but
contain also a fair proportion of albuminoids ; they may
be added to dry fodder without seriously affecting its
digestibility, if the albuminoid ratio of the whole food
does not fall below 1 : 8.*

Common salt is well known to be a useful addition to

* In this statement made by Wolff the whole of the nitrogen in the food
is reckoned as albuminoid.

86

THE CHEMISTRY OF THE FARM.

the food of animals. It does not apparently assist di-
gestion, but it increases appetite ; and when sodium salts
are deficient in the food, it supplies the blood with a ne-
cessaiy constituent. Sodium salts are tolerably abundant
in mangels, and small in quantity in hay ; they are absent
in potatos, and generally absent in grain of all kinds.

2. Experiments with Horses. — In recent experiments
conducted by Wolff the digestive powers of horses and
sheep have been accurately compared, the same food
having been supplied to each set of animals.

The principal results were as follows : —

EXPERIMENTS WITH HORSES.

Proportion of each constituent digested
for 100 supplied.

FOOD.

ill

III

1

Pasture grass
Meadow hay (very good) .
Meadow hay (ordhiaiy)
Lucerne hay . . .
Oats .'....
Beans ....
Maize

62-1
51-7
46-3
57-9
72-0
87-4
90-9

68-8
64-3

58-4
74-3
87-0
86-2
77-6

13-4
23-5

18-8
3-2

78-2
8-5

63-0

65-8
56-9
51-7
70-2
76-6
93-4
93-9

57-0
42-6
37-3
39-0
25-6
69-3
100-0

EXPERIMENTS WITH SHEEP.

Pasture gi-ass ....

75-8

73-3

65-4

75-7

79-5

Meadow hay (very good) . .

64-7

^^•Q

54-5

65-6

63-5

Meadow hay (ordinary) .

58-7

57-2

44-3

58-7

59-8

Lucerne hay . . . .

59-1

72-8

29-7

67-9

43-6

Oats

72-9

85-5

84-8

77-7

26-1

Beans

89-6

87-1

84-2

91-2

78-5

Maize

88-5

78-5

84-6

91-3

61-9

FOODS. 87

On comparing these figures it is evident that a horse
digests meadow grass and hay less perfectly than a sheep,
and the difference between them is apparently as great
■when the food is young grass as when ordinary hay is
employed. There is little difference in the proportion of
albuminoids assimilated by the two animals, but the
divergence becomes very considerable when we come to
the carbo-hydrates, fibre, and fat. Of the carbo-hydrates
the horse digests 7 — 10 per cent., of the fibre 22 per cent.,
and of the fat and waxy matter 25 — 52 per cent, less than
the sheep. On the whole, the horse digests about 12 per
cent, less of the total organic matter of grass hay than
the sheep. With lucerne hay of good quality the digestion
by the horse is far better, and (save as regards the fat)
nearly equals that of the sheep.

The small digestive power of the horse for vegetable
fibre is plainly connected with the fact that it is not like
the sheep a ruminant animal, and is thus unprovided
with the same means of attacking an insoluble food. In
a trial with wheat-straw chaff the horse digested 22'5.,
and the sheep 47'6 per cent, of the total organic
matter.

With corn the digestion of the horse is apparently quite
equal to that of the sheep. The beans and maize were
soaked in water before they were given to the horse.
Stress must not be laid on the digestion coefficients found
for ingredients of the food present in small quantity, as,
for instance, the fat and fibre of beans, and the fibre of
maize.

3. Experiments with Pigs. — These have not been so
numerous as those with ruminant animals. The following

88

THE CHEMISTRY OF THE FARM.

table shows the digestibility ascertained for some of the
common pig foods : —

EXPERIMENTS WITH PIGS.

Digested for 100 supplied.

Albumi-

Food.

Total
organic
matter.

Albumi-
noids.

Fat.

Solulile
carbo-
hydrates.

noid
ratio, t

*Sour milk
*Meat Hour .
Pea meal
Bean meal .
*Burley meal .
Maize meal
Eyo bran
Potatos .

97
92

91
84
84
91
67
94

96
97

88
79
79
84
66
81

95

87
68
71
70
76
58

99

97
91
90
94
75
98

1

2-3
0-4
2-5
2-6
7-0
8-8

9-2

The digestive power of the pig for the foods here men-
tioned is very considerable, and in cases admitting of
comparison appears to be fully equal to that possessed by
ruminant animals. Nor is the pig incapable of digesting
vegetable fibre, when this is presented in a favourable
condition. Two pigs fed on green oats and vetches di-
gested 48*9 per cent, of the fibre supplied. The digestive
apparatus of a pig is not, however, adapted for dealing
successfully with bulky fodder. Pigs are very capable of
digesting animal food.

4. Experiments with Geese. — These birds have no
power of digesting vegetable fibre ; the food apparently
passes too quickly through the system for the fibre to be
attacked.

• The numbers in this case are the result of a single experiment,
t These ratios refer to the part of the food actually digested.

FOODS. 89

Comparative K'utritive Value of Foods. — Having
made ourselves acquainted with the composition and
degree of digestibiUty of the ordinary cattler^55^~\V]E
now offer some oreneral considerations/^ to'theii
feeding value. f [i'^J'^y^ '^

1. Influence of proportion of Water.-*— ^h]8,ileedb?g

value of roots, and of other foods rich in waterj^*^ wteir',
diminished by the fact that a part of the heat they
produce in the body is consumed in raising the water they
supply to the temperature of the animal, and of vaporising
a part of it as perspiration. With sheep the normal pro-
portion of water to dry food is about 2:1; with cattle,
from whose skin perspiration is more active, about 4:1.

A sheep feeding on turnips in winter in the open field,
consuming, say, 20 lb, of roots per day, will receive in its
food about 18 lb. of water, of which 14 lb. is beyond that
necessary for nutrition. This 14 lb. of water has to be
raised from near the freezing point to the temperature of
the animal body, a rise of at least 60° Fahr. To warm the
water to this extent will require the combustion of about
54 grams of carbo-hydrates, reckoned as starch, equal to
about 6 per cent, of the total food consumed. The actual
waste of food will, however, considerably exceed this, as a
part of the extra water will be vaporised as perspiration,
and to vaporise 1 lb. of water at the temperature of the
animal body requires the combustion of 62 grams of starch.
The consumption of an excess of water will also slightly
increase the amount of albuminoids oxidised in the animal
body, and thus occasion a certain amount of waste of the
nitrogenous part of the food.

The economy of supplying sheep on roots or green fodder

90 THE CHEMISTRT OF THE FARM.

with dry food in addition is obvious from the facts just
stated ; by so doing the quantity of water consumed by
the animal is diminished, and its proportion in the diet
brought more nearly to a normal ratio.

2. Capacity for producing Heat and Work. — The

only basis on which the nutritive value of foods of different
composition can be compared is in respect to their
capacity for producing heat. The production of heat and
mechanical work is the principal result which food accom-
plishes in the animal body; the capacity for producing
heat also stands in a near relation to the capacity for
producing fat. On the other hand, the amount of heat
which any food is capable of producing stands in no rela-
tion to its power of increasing or renewing the nitrogenous
tissues of the body. We may, however, safely assert that
the amount of heat generated by the combustion of the
digestible constituents of any food will be a fair guide to
its nutritive value, when the diet of which it forms a part
supplies a sufficient amount of digestible albuminoids, and
this will be the case whenever foods are skilfully used.

According to Frankland's actual determinations of the
heat-producing power of fat, albumin, and starch, their
comparative values in this respect are 100, 47*4, and 431.
The albumin is here reckoned as minus its equivalent
quantity of urea, as this product of the decomposition of
albumin is not burnt, but excreted by the kidneys. If,
now, we take the proportions of digestible fat, albu-
minoids, carbo-hydrates and cellulose, supplied by any
food, and multiply them by the heat coefficients just given,
the sum of the products will represent the heat-producing
capacity of the food when consumed in the animal body.

FOODS.

91

Taking the heat-producing capacity of maize, calculated
in this manner, as 100, the values found for other foods-
will be as follows : —

COMPARATIVE HEAT-PRODUCING VALUE OF FOODS.

Ordinary
conditiou.

Perfectly diy.

Maize .....
Linseed cake ....
Beans .....

Barley

Oats

Wheat bran ....
Meadow hay ....
Wheat straw ....

Potatos

Mangels

100
95
93

85
80
67
59
47
30
13

100
96
96
88
81
69
61
49
105
100

These figures are to be taken only as approximations to
the truth ; their correctness mainly depends upon the-
accuracy of the digestion experiments with ruminant
animals described in the last section. The fio;ures given
for those foods containing amides, and salts of organic
acids, are undoubtedly too high. Linseed cake, from the
large proportion of fat and albuminoids wliich it contains,
would be expected to occupy a much higher position in
the table ; its lower rank is due to its imperfect digesti-
bility. The table on page 80 shows that while 20 per
cent, of linseed cake remains undigested, and therefore
useless to the animal, only 12 per cent, of maize, and 10
per cent, of beans are thus wasted.

The general result is to show that the heat and work
producing power of the more perfectly digested foods is
nearly equal, if we assume the same quantity of dry food
to be supplied in each case.

We should gather from these calculations that an equal

92

THE CHEMISTRY OF THE FARM.

weight of maize, beans, or linseed cake will have a nearly
similar feeding value if supplied to an animal receiving a
sufficient amount of albuminoids in its diet, as for example
if given to a sheep fed on good meadow or clover hay.

3. Proportion of Albuminoids to Non-Albuminoids. —

A further point of great importance in determining the
value of a food is the proportion between the digestible
albuminoids, and the digestible non-nitrogenous con-
stituents : this relation we have already termed the " albu-
minoid ratio " of the food. In calculating this relation the
whole of the non-nitrogenous ingredients of the food are
first reduced, as already explained, to their equivalent in
starch. Taking the average composition of foods already
given, and the digestibility of their constituents shown by
the German experiments, the albuminoid ratios will be as
under : —

PROPORTION OF NITROGENOUS TO NON-NITROGENOUS CON-
STITUENTS IN THE DIGESTIBLE PART OF FOOD.

Cotton cake, decorticated .
Cotton cake, undecorticated
Linseed cake
Beans .

Wheat bran
Oats
Barley
Maize

Clover hay .
Meadow hay
Swedes
Turnips .
Mangels
Potatos .
Wheat straw

Total nitrogen
reckoned.

Amides, &c., not
reckoned.

1-5
1-8
2-3
2-4
2-9
4-2
5-5
7-6
9-0
5-9
8-0
5-9
6-2
8-0
10-6
64-4

?

12-4
13-1
t

31-8
17-7
i

FOODS. 93

In the first column the whole of the nitrogen in the
food is reckoned as existing as albuminoids; in the second
column the true albuminoids only are taken account of.
In calculating the second column it has been assumed
that in a digestion experiment the amides and nitrates,
being soluble bodies, would be reckoned as "digestible
albumin ; " the amides have not, however, been reckoned
among the non-albuminous constituents, their equivalent
in starch not being yet known.

The fissures show in a strikino^ manner the wide differ-
ences that exist among foods as to the proportion of
albuminoids which they supjDly, the difference being made
still more considerable by the recent discovery that a large
part of the nitrogen in certain foods exists as amides and
not as albuminoids. Mangels now appear as a food very
poor in albuminoids, whereas they were formerly supposed
to supply a sufficient proportion ; and the same is doubt-
less true of other roots not yet thoroughly examined.

The poverty of a diet of roots and straw chaff in
digestible albuminoids is the true reason of the excellent
effects produced by the addition of oilcake or leguminous
corn. Oilcake and beans used under these circumstances
have an effect far above their own intrinsic feeding value,
as their presence raises the character of the whole diet,
and enables the carbo-hydrates of the roots and straw to
contribute to the formation of carcase.

It must be recollected that the albuminoid ratio of a
food may be different for different animals if their powers
of digestion are unequal. Thus the same meadow hay
supplied to sheep and horses had for the former an albu-
minoid ratio of 1 : 9'1, and for the latter a ratio of 1 : G"7.
The horse, as we have seen, digests the nitrogenous con-

94 THE CHEMISTRY OF THE FARM.

stituents of hay nearly as well as the sheep, but fails in
digesting the non-nitrogenous constituents. Hay is thus
a more nitrogenous food for horses than for sheep.

The proportion of albuminoids most suitable for various
diets will come under consideration in the next chapter.

General Conclnsions. — We have now run through the
principal points which determine the value of food. A
little consideration will, however, show that it is impossible
to affix a definite feeding value to any food, as its practical
effect must depend in great measure on the conditions
under which it is employed ; more especially on the kind
•of animal consuming it, and the general character of the
diet of which it forms a part. Thus, the value of a bulky
food, as hay or straw, is far greater when given to a
ruminant animal, than when consumed by a horse or pig.
Concentrated, easily digestible foods, as com and oilcake,
have clearly a value above their composition when added
to a poor and bulky food, as straw chaff, or to a watery
food like turnips, because they are the means of raising the
diet to a point at which the animal will thrive. On the
■other hand, roots and green fodder, even when watery and
poor in composition, may have a considerable effect when
added in moderate proportion to dry food. The highest
value is, in short, only obtained from food when it is
skilfully employed.

There is, finally, a condition which we can never hope
to express by figures, but which has a considerable influence
on the effect of any diet ; this is flavour. An agreeable
flavour stimulates appetite, and probably promotes
digestion. This part of the question belongs, however,
rather to practice than science.

CHAPTER VIIL

RELATION OF FOOD TO ANIMAL REQUIREMENTS.

The Requirements of the Young Animal. — Composition of colostrum and
milk — Suitable albuminoid ratio of the food. The Adult Animal. —
Work, how performed — Maintenance diets — Labour diet. Tlte Fat-
tening Animal. — Conditions necessary for increase — Eesults obtained
when fattening oxen, sheep, and pigs, on ordinary diets — Alterations
in consumption of food, and rate of increase, as fattening proceeds —
Albuminoid ratios for fattening animals. Production of Wool. — Com-
position of wool — Influence of diet. Production of Milk. — In-
fluence of diet on the quantity and quality of the milk — Influence on.
the character of the butter — Albuminoid ratio for milk-cows.

The Young Growing Animal. — The special character
of the nutrition of young animals is the rapid formation
of nitrogenous tissue and bone, for which purpose an
abundant supply of albuminoids and ash constituents in
the food is clearly requisite.

The kind of food most appropriate to the wants of a
young animal is shown by the composition of milk. The
milk supplied to the young immediately after birth (the
colostrum) is of a very concentrated description. During
the first week after birth the quantity of the milk greatly
increases, and its composition gradually alters from that
of colostrum to that of ordinary milk.

In the following table will be found the composition of
the colostrum and milk yielded by various farm animals ;
the numbers given are the mean of many analyses.

96

THE CHEMISTRY OF THE FARM.

COMPOSITION OF COLOSTRUM.

Ill

Water.

Albumi-
noids.

Fat.

Sugar.

Ash.

Albuminoid
ratio.*

73-2
70-1

71-7

15-4
15-6
20-7

2-0
9-5
3-4

8-0
3-8
2-5

1-4 1 1:0-8
0-9 1:1-7
1-8 1:0-5

COMPOSITION OF MILK.

Ewe . . .

83-1

5-5

5-5

5-0

0-9

1:3-3

Sow .

84-6

6-3

4-8

3-4

0-9

1 :2-3

Goat . . .

85-3

4-1

5-2

4-6

0-8

1:4-1

Cow .

87-0

4-0

3-7

4-6

0-7

1 : 3-3

Ass. . . .

90-0

2-3

1-3

6-0

0-4

1:3-7

Mare .

90-4

2-0

1-0

6-2

0-4

1 : 4-0

The colostrum is characterised by an especially high
percentage of albuminoids. In milk we find a smaller
proportion of albuminoids, and a larger proportion of fat
and sugar. The solid matter of milk has a very high
feeding value, owing to the large proportion of fat and
albuminoids present, and its perfect digestibility. If we
take, as before, the heat-producing capacity of dry maize
as 100, then the heat-producing capacity of dry cow's milk
will be 140. Milk also supplies the ash constituents
necessary for the formation of bone and tissue : 100 lb. of
cow's milk will supply about 0*20 lb. of phosphoric acid,
016 lb. of lime, and O'lT lb. of potash.

The relation of the nitrogenous to the non- nitrogenous
constituents of milk is much higher than in most vegetable
foods ; the analyses in the table show a relation varying

In calculating this relation it has been assumed that 10 of milk sugar
are equivalent to 9 of starch.

RELATION OF FOOD TO ANIMAL REQUIREMENTS. 97

from 1 : 2'3 to 1 : 41, and the latter proportion is seldom
much exceeded in any sample of milk. In supplying very
young animals with artificial food the above facts must be
borne in mind ; the food should clearly be of an easily
digestible character, and contain a considerable proportion
of albuminoids and fat. Instead of this, foods rich in
starch are too often employed. Linseed is perhaps, of
ordinary foods, the one most similar to milk in composition.
As the animal grows the quantity of food it requires
increases, at the same time a larger proportion of the food
is applied to the production of heat and mechanical work ;
the proportion of nitrogenous matter in the food may
therefore gradually be diminished, carbo-hydrates and fat
being quite as fit as albuminoids for producing heat and
work. Under natural conditions this diminution in the
nitrogenous character of the diet soon takes place, the
animal daily taking more and more grass in addition to
its mother's milk. The albuminoid ratio * of the diet of
rapidly growing animals may vary from 1 : 5 to 1 : 7, the
more nitrogenous diet being most suitable for younger
animals, or for the production of more rapid increase.

The adult Animal. — Food, we have already seen, is
primarily employed for the renovation of the animal
tissues, and for the production of heat and mechanical
work ; by far the greater portion of the food is applied to
the latter purposes.

Much of the work performed by an animal is internal,
and consists in the muscular movements which produce

* The albuminoid ratios henceforward given will represent, as far as pos-
sible, the proportion of true albuminoids present in the food.

I H

98 THE CHEMISTRY OF THE FARM.

circulation, respiration, and other vital processes; such
work is carried on even when the animal is at rest. In
man the whole of the blood is pumped through the heart
every half minute. The daily work performed by the
heart of an average man has been calculated as equal to
150 — 200 foot-tons ; that is to say, the power exerted by
the heart would raise 1 ton to the height of 150—200 feet.
The work performed by other organs, and by the muscles
when merely maintaining the body in an erect position,
has not yet been satisfactorily measured.

It was formerly supposed that muscular force was
produced by the oxidation of the muscle, and that a diet
rich in albuminoids was consequently necessary if hard
labour was to be maintained. This idea is now known to
be erroneous, it having been shown by repeated experi-
ments that labour does not necessarily increase the pro-
duction of urea, while it does in every case greatly
augment the amount of carbonic acid and water exhaled.
Mechanical power is, in fact, produced not by oxidation
of the muscle, but of the organic matter in circulation ;
this organic matter may be indifferently either fat, carbo-
hydrates, or albuminoids. The animal body thus obtains
the power necessary for the performance of work in the
same manner as a steam engine, only that in the body
food is burnt in the place of coal.

When labour is demanded from an under-fed animal,
the oxidation taking place in the circulatory system may
be in excess of the food supplied, and of the fat and carbo-
hydrates in circulation ; in such a case the albuminoids
of the animal body are oxidised, and the excretion of urea
becomes increased. A working animal ill supplied with
food will thus suffer seriously in condition.

RELATION OF FOOD TO ANIMAL REQUIREMENTS. 90

In the case of an adult animal not increasing in weight,
and performing a minimum amount of work, as, for
instance, a horse or ox in a stable, the quantity of food
required is reduced to its smallest limits. An ox of 1000 lb.
live weight, quiet in the stall, will require daily, according
to the German experiments, about 0*5 — 0*6 lb. of digestible
albuminoids,* and 7'1 — 8*4 lb. of digestible non-albuminous
food, reckoned as starch, to preserve its condition. With
sheep the maintenance diet must be more liberal, as in
their case the growth of wool, with its accompanying fat,
is always in progress, and is practically independent of
the abundance or poverty of the diet. For 1000 lb. live
weight (shorn), sheep fed on meadow hay will require
about 0*9 lb. of digestible albuminoids,* and 10*8 lb. of
digestible non-albuminous food, or 16 — 17 lb. dry organic
matter, per day, to preserve their condition. If fed on
mangels and straw chaff the quantity of dry organic matter
must be raised to 20 — 25 lb. In these maintenance diets
for adult animals the albuminoid ratio of the food is but
1 : 14 in the case of the ox, 1 : 12 in the case of the sheep
fed on hay, and the relation is wdder still in the case of
the sheep fed on straw and mangels. The inferiority of
the latter diet is the cause doubtless of the larger amount
of food required.

If external work is to be performed, the body weight
remaining unaltered, the quantity of food must be con-
siderably increased, and the food must be of such quality
that it may be possible to digest a sufficient amount in
the required time. A man doing a fair day's work was

* These numbers represent true albuminoids, and are, therefore, smaller
than the German figures.

H 2

100 THE CHEMISTRY OF THE FARM.

found to exhale one-third more carbonic acid than when
at rest ; a man doing such work would clearly require
one-third more food to maintain the same condition of
body.

If we assume that when food is burnt in the body one-
fifth of the energy developed may appear as external
work, then 1 lb. of digested starch would enable an
animal to perform 485 foot-tons of work, 1 lb. of digested
albumin 528 foot-tons, and 1 lb. of digested fat 1127 foot-
tons of work.

The recent experience of the use of maize for horses
shows that an albuminoid ratio of 1 : 9 is quite sufficient
for a labour diet.

The Fattening Animal. — The character of the fattening
process has been more thoroughly studied than the
nutrition of young and growing animals.

For the body to increase in weight it is clear that the
food supplied must be in excess of the quantity demanded
for mere renovation of tissue, and for the production of
heat and work. When such an excess of food is given, a
pai-t of the albuminoids and ash constituents is generally
converted into new tissue, while a part of the fat, carbo-
hydrates, and albuminoids is stored up in the form of fat.

As ouly the excess of the food is converted into increase,
liberal feeding is, within certain limits, the most economical.
If a lamb can be brought by liberal treatment to 150 lb.
live weight at one year old, the amount of food consumed
will be far smaller than if two years are occupied in
attaining the same weight, for the food required for
animal heat and work during the second year is clearly
saved.

RELATION OF FOOD TO ANIMAL REQUIREMENTS. 101

Economy of food is also promoted by diminishing
the demand for heat and work. An animal at rest in a
stall will increase in weight far more than an animal
taking active exercise on the same diet. In the same
way the increase from a given weight of food will be less
in winter than in spring or autumn, a far larger proportion
of the food being consumed for the production of heat
when the animal is living in a cold atmosphere. Hence
the economy of feeding animals under cover during winter.
If, however, the temperature becomes so high as to con-
siderably increase the perspiration, waste of food again
takes place, heat being consumed in the evaporation of
water. The temperature most favourable for animal
increase is apparently about 60° Fahr. Quietness, and
freedom from excitement are essential to rapid fattening ;
the absence of strong light is therefore desirable.

The capacity of an animal for fattening depends much
on breed and temperament. A farmer learns to recognise
the fattening disposition of an animal from the feel of its
skin, &c.

The three animals with which the farmer is chiefly con-
oerned have very different powers of consuming food, and
yield different rates of increase. Lawes and Gilbert reckon
that, on an average of the whole fattening period, an ox
will produce 100 lb. of live weight from the consumption
of 250 lb. oilcake, 600 lb. clover hay, and 3500 lb. swedes.
Sheep will produce the same increase by the consumption
of 250 lb. oilcake, 300 lb. clover hay, and 4000 lb.
swedes. Pigs will require about 500 lb. of barley meal to
yield a similar result. Taking these data, the rate of
food consumption, and of increase yielded will be as
follows : —

10:

THE CHEMISTRY OF THE FARM.

RESULTS OBTAINED WITH FATTEXING ANIMALS
PER 100 LB. LIVE WEIGHT PER WEEK.

Oxen

Sheep ....

Pigs

Received by the
animal.

Results produced.

Total
dry food.

Digestible
oi-ganic
matter.

Pood
consumed
for heat

and
work.*

D.y

manure

producetLt

Increase
in live
weight.

lb.
12-5
16-0
27-0

lb.

8-9
12-3
22-0

lb.

6-86

9-06

12-58

lb.
4-56
5-10
4-51

lb.
1-13

1-76
6-43

RESULTS OBTAINED IN RELATION TO FOOD CONSUMED.

Oxen

Sheep ....

Pigs

Increase in live
weight.

On 100 lb. of dry food.

Per

100 lb.

dry food.

Per

100 lb.
digested
organic
matter.

Consumed

for heat

and

work.*

Drj'

maimre

produced, t

T)ry
increase
yielded.

lb.

90
11-0
23-8

lb.
12-7
14-3

29-2

lb.
54-9
56-6
46-6

lb.
36-5
31-9

16-7

lb.
6-2

8-0
17-6

It is evident from the upper division of the table that
pigs are able to consume far more food in proportion to
their weight than either sheep or oxen. This is due to
the concentrated and digestible character of the food (corn
meal) supplied to a fattening pig, and to the great
capacity of this animal for assimilation. The proportion

* In calculating the amount of food consumed for the production of heat
and work, it has been assumed that the fat in the increase has been derived
entirely from the fat and carbo-hydrates supplied by the food.

f The manure is exclusive of litter.

EELATION OF FOOD TO ANIMAL EEQUIREMENTS. 103

of stomach is greater in a fat ox or sheep than in a pig,
being on 100 lb. live weight, 3 "2 for the ox, 2 '5 for the
sheep, and 07 for the pig. On the other hand, the pro-
portion of the intestines is greater with the pig than with
sheep or oxen. Ruminant animals are thus best fitted for
dealing with food requiring a prolonged digestion, while
the pig excels in the capacity for assimilation.

As a natural result of the larger consumption of food
the pig increases in weight much more speedily than
either the sheep or ox ; but not only is the rate of
increase more rapid, the increase yielded by the pig is
also far greater in proportion to the food received, as
plainly appears from the lower division of the table. The
pig with its very large consumption of food has, in fact, to
spend a smaller proportion of it on heat and work, and
has thus a large surplus left to store up as increase. Of
100 lb. digested organic matter, the fattening ox spends
about 77 for heat and work, the sheep 74, and the pig 57.
The upper division of the table shows, however, that in a
given time a pig does convert a much larger amount of
food into heat and work than either sheep or ox ; this
greater consumption probably represents internal work
performed in the laying on of increase. The pig, with its
rapid feeding, and high rate of increase, is undoubtedly
the most economical meat-making machine at the farmer's
disposal.

The results given by sheep are seen to lie in nearly
every case between those given by oxen and pigs, being
however much nearer to the former than to the latter.
The German experiments place the sheep below the ox as
an economic producer of increase, instead of above it, as
in the Rothamsted statistics just quoted ; the difference is

104 THE CHEMISTRY OF THE FARM.

probably due to the different breeds of animals experi-
mented with. The influence both of breed, and of the
individual character of the animal on the rate of increase
whilst fattening is very considerable.

The results relating to manure will be discussed in the
next chapter.

We have hitherto looked at the fattening period as a
whole ; the rates of consumption and of increase are,
however, very different in different stages of this period.

As a fattening animal increases in size the quantity of
food it consumes also somewhat increases, the require-
ments of the body for heat and renovation of tissue
becoming greater as its weight and size are increased ; the
stomach at the same time becomes larger. When the animal
becomes very fat, the consumption of food falls off again,
the rate of increase at this point being much diminished.

As fattening advances the daily increase in live weight
becomes gradually smaller, and the same amount of food
will 2^roduce a steadily diminishing amount of increase.
This is partly because the increase during the later stages
of fattening is drier, and contains a larger proportion of
fat than in the earlier stages of the process. Partly also
because the consumption of food for heat and work is
increased with the increasing size of the body. More
internal work must also be performed to add increase to a
large animal than to a small one. These changes in the
rates of consumption and increase are seen more strikingly
in the case of pigs than with other animals, from the
greater rapidity of the fattening process. The following
table shows the average results obtained on sixteen pigs
fattened at Rothamsted at the same time, the food being
7 lb. of pea meal per head per week, with an unlimited

RELATION OF FOOD TO ANIMAL REQUIREMENTS. 107

unwashed fleece ; but in the case of ordinary sheep, freely
exposed to weather, the quantity may be 15 per cent., or
less. In a washed fleece the fat may vary from more than
30 per cent, to 8 per cent., or less. Short fine wool con-
tains the largest proportion of fat. Pure wool hair con-
tains about 16 per cent, of nitrogen. The quantity of
nitrogen and ash constituents in unwashed wool has been
already given on page 63.

The production of wool-hair and of wool-fat is practi-
cally no greater when sheep receive a liberal fattening
diet, than when the diet only suffices to maintain the
ordinary condition of the animal; indeed, under poor
treatment, the carcase may lose weight to some extent
without the production of wool being seriously altered.
With starvation, however, the yield of wool is considerably
diminished. If sheep are kept on a poor diet for the
mere production of wool, the amount of albuminoids sup-
plied must not fall too low, wool-hair being formed entirely
from this part of the food.

Production of Milk. — The quantity of milk produced
is largely determined by the individual character of the
animal, and on the length of time which has elapsed since
birth ; the quality of the milk is also affected, though to-
a less extent, by the same conditions. Subject to these
natural limitations, both quantity and quality are greatly
influenced by the character of the food supplied.

A liberal diet is essential for a full supply of milk.
Green fodder is favourable to a large produce, so also are
brewers' grains. The diet of a milking cow should vary
with the yield of milk, the object being to obtain as large
a yield as can be reached without fattening the animal.

108 THE CHEMISTRY OF THE FARM.

The quality of the milk is considerably influenced by
the richness of the diet. A diet of watery grass will pro-
bably yield a moderate quantity of poor milk, the addition
of oilcake will increase both the yield of milk and also its
richness. The alteration in the composition of milk by
poor or liberal feeding is chiefly an alteration in the per-
centage of solid matter ; the relative proportions of casein,
butter, and sugar are scarcely affected by the character of
the diet.

The quality of the butter is more or less influenced by
the character of the food, some foods producing a hard,
and others a soft butter. Rape cake, oats, and wheat
bran are reckoned in Denmark as first-class butter foods :
palm nut cake and barley as second-class foods ; while
linseed cake, peas, and rye are placed in the third class.
The first-class foods produce a soft butter, the third class
foods a hard butter. By the employment of first and
second class foods with straw chaff, hay, and roots, an
abundance of excellent butter may be produced through-
out the winter. Turnips strongly flavour both milk and
butter ; mangels are a better food for milk cows.

As milk is a product far more nitrogenous than the
increase of carcase obtained when an animal is fattened,
cows in full milk will require a tolerably nitrogenous diet.
Such a diet is naturally provided when cows feed on young
grass and clover; when hay, straw, and roots form the
bulk of the food, it is imperative that cake or corn be also
employed if abundance of milk is desired. Wolff gives
1 : 5 as the albuminoid ratio most suitable for the diet of
cows in full milk : deducting amides, the ratio will pro-
bably be about 1 : 6 — 7.

CHAPTER IX.

RELATION OF FOOD TO MANURE.

The quantity of manure produced by oxen, sheep, and pigs, under given
diets — Proportion of the ash constituents and nitrogen of the food
which appears in the liquid and solid excrements — Composition of
the excrements of sheep and oxen — The relative manure value of
various cattle foods— The value of the ash constituents and nitrogen
of animal manure as compared with the same materials in artificial
manures.

The quantity of dry manure produced for a given
quantity of food consumed has been already mentioned.
The figures in the table on p. 102 show that, with the diets
assumed, the sheep produces for the same weight of dry
food nearly twice as much manure as the pig, while the
ox produces even more manure than the sheep. This dif-
ference is due to the less digestible character of the food
supplied to the sheep and ox. The quantity of manure
produced during the same time, and for the same body
weight, is however very similar with the three animals,
the greater consumption of food by the pig counter-
balancing its lower rate of manure production.

The only constituents of food which are of importance
as ingredients of manure are the nitrogenous substances,
and the ash constituents. If the live weight of an animal
remains unchanged, and there is no production of milk,
the quantity of nitrogen and ash constituents voided in

110 THE CHEMISTRY OF THE FARM.

the manure will be the same as that contained in the food
consumed ; the albuminoids and ash constituents of the
food used for the renovation of tissue being in this case
equivalent to the quantity yielded by the degradation of
tissue. In cases where the body weight is increasing, or
milk is being produced, the amount of nitrogen and ash
constituents in the manure will be less than that in the
food in direct proportion to the quantity of these substances
which has been converted into animal produce.

A part of the albuminoids and ash constituents is left
undigested during the passage of the food through the
alimentary canal ; these are voided in the solid excrement.
The digested nitrogenous matter and ash constituents
pass into the^blood, a part of them may be converted into
animal increase if the animal is gaining in weight or pro-
ducing milk, and the remainder is finally separated from
the blood by the kidneys, and is voided in the form of
urine. The albuminoids and amides are oxidised into urea
before being expelled from the system. In the case of
herbivorous animals hippuric acid is also formed in vari-
al:^le quantities, and is found as an ingredient of the
urine.

The proportion of the nitrogen in the food which will
appear in the solid excrement is determined by the diges-
tion coefficient of the albuminoids. Thus 79 has been
already given as the digestion coefficient of the albumi-
noids of barley meal when consumed by a pig ; it follows
that in this case for 100 of albuminoids consumed 21 will
be voided in the solid excrement, and 79 pass into the
blood. It has been already stated that 500 lb. of barley
meal, containing about 53 lb. of albuminoids, will in the
case of the pig produce 100 lb. of animal increase, con-

RELATION OF FOOD TO MANURE.

Ill

taining 7'8 lb. of albuminoids. It follows from these data
that for 100 lb. of albuminoids consumed, 14*7 are stored
up as carcase, 21 appear in the solid excrement, and 64'3
as urea, &c., in the urine. In the same way, by deduct-
ing the ash constituents stored up from those present in
the food, we can arrive at the quantity of ash constituents
voided in the manure. Calculating in this manner the
relation of food to manure in the case of the fattening ox,
sheep, and pig receiving the diets assumed in previous
calculations (p. 101), we arrive at the following con-
clusions : —

NITROGEN STORED UP AND VOIDED FOR 100 CONSUMED.

Oxen ....

Sheep

Pigs ....

Stored

up as

increase.

Voided

as solid

excrement*

Voided

as licjuid

excrement.

In total
excrement.

3-9

4-3

14-7

22-6
167
21-0

73-5
79-0
64-3

96-1
95-7
85-3

ASH CONSTITUENTS STORED UP AND VOIDED FOR
100 CONSUMED.

Oxen
Sheep
Pigs

Stored up as
increase.

2-3

3-8
4-5

Voided in total
excrements.

97-7
96-2
95-5

The proportion of the nitrogen and ash constituents of

* The quantities of nitrogen given in this cokimn are a little below the
truth, as besides the undigested albuminoids some nitrogenous biliary matter
is present in the solid excrement. With oxen and sheep the amount of biliary
matter in the excrement is very small ; with pigs it is more considerable. In
the case of the pig the nitrogen in the solid excrement should probably stand
as 25 '0, and that in the liquid as 59 '3.

112 THE CHEMISTRY OF THE FARM.

the food which is stored up in the body of a fattening
animal is in all cases very small. In the case of each
animal mentioned in the above tables more than 95 per
cent, of the ash constituents of the food find their way
into the manure. With oxen and sheep more than 95
per cent, of the nitrogen of the food are likewise thus
voided. The pig is seen to retain the largest proportion
of the nitrogen of its food ; this is clearly owing to the
greater proportion of increase which the pig produces for
a given weight of food consumed.

The amount of nitrogen voided in the urine is seen to
be three or four times the quantity contained in the solid
excrement. This relation will vary greatly according to
the character of the diet. If the food is nitrogenous, and
easily digested, the nitrogen in the urine will greatly pre-
ponderate ; if, on the other hand, the food is one imper-
fectly digested, the nitrogen in the solid excrement may
form the larger quantity. When ordinary hay is the diet,
the nitrogen in the solid excrement will generally some-
what exceed that contained in the urine ; with a straw
diet the excess in the solid excrement will be much
greater. On the other hand, corn and cake, and especially
roots, yield a large excess of nitrogen in the urine.

The ash constituents are very differently distributed in
the solid excrement and urine ; in the former the lime,
magnesia, and phosphoric acid are chiefly found, while
the latter contains nearly all the potash. With sheep fed
on hay, about 95 per cent, of the lime contained in the
food, 70 per cent, of the magnesia, and 83 per cent, of the
phosphoric acid were found in the solid excrement, but
only 8 per cent, of the potash.

A fair idea of the general composition of the solid excre-

RELATION OF FOOD TO MANURE.

113

ment and of tlie urine, is given by the following table.
The sheep were fed on meadow hay ; the oxen on clover-
hay, and oat straw, with about 8 lb. of beans per day.

PERCENTAGE COMPOSITION OF SOLID AND LIQUID EXCREMENT.
SHEEP FED ON HAY.

Water

Orj^anic matter

Ash

Solid excrement.

Urine.

Fresh.

Dry.

Fresh.

Dry.

66-2

30-3

3-5

S9-6
10-4

85-7
8-7
5-6

61 -0
39-0

Nitrogen

07

2-0

1-4

9-6

OXEN WITH NITROGENOUS DIET.

Water

Organic matter

Ash

Solid excrement.

Urine.

Fresh.

Diy.

Fresh.

Dry.

86-3

12-3

1-4

89 -7
10-3

94-1
3-7

2-2

63'0
37-0

Nitrogen . . . .

0-3

1-9

1-2

20-6

Both the solid and liquid excrements of the sheep are
far drier, and therefore more concentrated, than those
of the ox, whose food includes a much larger quantity of
water.

The extreme richness of the urine, both in ash con-
stituents and nitrogen, is very evident. In the case of
the more highly-fed oxen, the dry matter of the urine is
seen to contain over 20 per cent, of nitrogen.

114

THE CHEMISTRY OF THE FARM.

The relative value of the manure produced by different
foods is determined by the relative richness of the foods
in nitrogen and ash constituents, but chiefly by the amount
of nitrogen, this being the most costly ingredient of pur-
chased manure. The average amount of nitrogen, and of
the two most important ash constituents contained in
ordinary cattle foods, is shown in the following table : —

MANURIAL CONSTITUENTS IN 1000 PARTS OF ORDINARY FOODS.

Cotton cake (clecorticatetl) . .

Dry
matter.

NitroKcn.

Potosh.

Phos-
l>horic
acid.

900

66-0

15-0 ?

31-2

Rape cake ....

900

48-0

13-2

24-6

Linseed cake . ...

880

45-0

14-7

19-6

Cotton cake (unclecorticated) .

885

39-0

20-1

22-9

liinseed

905

36-0

12-3

15-4

Palm-kerael meal (English) .

930

25-0

5-5

12-2

Beans

855

41-0

]2-0

11-6

Peas

857

36-0

9-8

8-8

Malt dust

905

38-0

19-5

17-2

Bran

865

22-0

14-8

323

Oats

870

20-6

4-5

6-2

Wheat

856

18-8

5-4

8-0

Barley

860

17-0

4-9

7-3

Maize . . .

886

16-6

3-6

61

Clover hay

840

19-7

19-5

5-6

Meadow hay ....

857

15-5

16-8

3-8

Bean straw . . . .

840

10-0

25-9

4-1

Wheat straw ....

857

4-8

5-8

2-6

Barley straw ....

850

5-0

9-7

2-0

Oat straw ....

830

5-0

10-4

2-5

Potatos

250

3-4

5-6

1-8

Mangels

115

1-9

3-9

0-7

Swedes

107

2-4

2-0

0-6

CaiTots

142

1-6

3-2

1-0

Turnips

83

1-8

2-9

0-6

1

RELATION OF FOOD TO MANURE. 115

The oilcakes yield the richest manure, as they contain
the largest amount of nitrogen and phosphoric acid, with
a considerable amount of potash. Next to these come the
leguminous seeds, malt-dust, and bran. Clover hay yields
a richer manure than the cereal grains, while meadow hay
stands below them. The cereal grains and the roots con-
tain about the same proportion of nitrogen in their dry
substance; the roots, however, supply much more potash.
Potatos stand below roots in manurial value. Straw takes
the lowest place as a manure -yielding food ; bean and pea
straw are more valuable for this purpose than the straw of
the cereals.

The ash constituents present in animal manure have
probably the full money value of the same constituents in
artificial manures, but the nitrogen has on the whole a
lower value than the nitrogen of ammonium salts or nitrate
of sodium. The nitrogen of the urine is indeed quite as
valuable as the nitrogen of ammonium salts. When
applied to soil the nitrogen of urine is rapidly converted
into nitrates, the form of nitrogen most suitable for plant
nourishment. But, on the other hand, the nitrogen of
the solid excrements is not in a form suitable for plant
food, and will be very slowly converted into nitrates in
the soil.

Animal manure is probably more immediately available
for the use of plants when applied directly to the land,
than when previously mixed with a great bulk of litter.
Fermentation with litter probably results in the formation
of nitrogenous humus compounds, which are insoluble,
and decompose but slowly in the soil.

The feeding of animals on the land is a mode of applying

I 2

116 THE CHEMISTRY OF THE FARM.

manure which has many advantages ; but the distribution
of the manure is in this case irregular, and if carried
out in autumn or winter the manure is subject to loss
by drainage. The most effective plan of application is
doubtless as liquid manure to growing crops. In winter
time, however, the use of litter, and the preparation of
farmyard manure (best under cover), becomes a necessity,
and is on the whole the best course to adopt.

CHAPTER X.

THE DAIRY.

The constituents of milk — The conditions affecting its richness — The fat
glohules — Modes of raising cream — Composition of cream — Composi-
tion of skim-milk — Churning — Composition of butter — Butter-milk
— Manufacture of cheese — Composition of cheese — Whey — Necessity
for cleanliness.

Milk — The general composition of colostrum, and of
ordinary cow's milk, has been already given on p. 96.

The albuminoids of milk embrace two constituents of
similar composition, casein and albumin. Casein is coagu-
lated by the addition of acids, or by rennet, but not by
boiling. Albumin is not coagulated by rennet, or by most
acids, but is coagulated by heat. In colostrum albumin
largely preponderates, so that the milk coagulates on
boiling ; in ordinary cow's milk the albumin forms but
one-ninth of the total albuminoids.

The fat of milk chiefly consists of the glycerides of
palmitic and oleic acid. The glycerides of stearic, myristic,
lauric, capric, capryllic, caproic, and butyric acid are also
present in small quantity. The last four of these acids
are, when in the free state, more or less soluble in water.
The glycerides of oleic acid and of the soluble fatty acids, are
fluid fats at ordinary temperatures, the remaining fats are
solid. The proportion of fluid and solid fats varies some-

118 THE CHEMISTRY OF THE FARM.

what with the diet and condition of the animal ; in summer
time the proportion of fluid fats is greater than in winter.

The sugar contained in milk is known by chemists as
lactose. When milk turns sour the lactose is converted
into lactic acid ; this acidification of the milk induces the
coagulation of the casein, and the milk curdles. The
ordinary souring of milk is the work of a ferment, Bacte-
rium lactis; when this ferment is excluded no souring
takes place.

Cow's milk has generally a specific gravity between
1*028 and 1*032. As the removal of cream raises the
specific gravity, which can be brought back to the normal
point by the addition of water, no safe conclusion as to the
quality of milk can be based on this indication.

The composition of cow's milk is affected by various
circumstances ; under extreme conditions it may contain
from 10 to IG per cent, of dry matter. The milk is poorer
when the quantity produced is large, or the diet insuffi-
cient, and richer when these conditions are reversed. A
cow is generally in full milk from the second to the
seventh week after calving; after this period the milk
gradually diminishes in quantity, but increases in rich-
ness. A separation of cream takes place in the udder ;
the milk first drawn is poor in fat, and the richness in-
creases as milking proceeds, the last drawn milk containing
two or three times as much fat as the first drawn. The
milk of old cows is said to be poorer than the milk of
young cows.

The relation of food to the production of milk and
butter has been already considered (p. 107).

Cream. — The fat of milk occurs in the form of globules ;

THE DAIKY. 119

the largest are about '0005 to 'OOOG inch in diameter, the
smallest may be one-tenth this diameter, or even less.
The average size of the globules is different with different
breeds of cattle. The size appears to diminsh as the time
from calving increases. The fat globules are in most
cases coated with a thin albuminous covering. As the fat
globules have a lower specific gravity than the serum in
which they float, they tend to rise to ,the surface, where
they form a layer of cream. The largest globules are the
first to rise, the smallest never rise at all, being too heavily
weighted by their albuminous covering. Milk containing
an abundance of large globules is best for butter-making,
as the cream then quickly and perfectly rises ; but milk
with small globules is probably best for cheese-making,
as a more even distribution of fat throughout the curd is
then obtained.

Milk, when it leaves the cow, will have a temperature
of about 90° Fahr. ; when set for cream it should be cooled
as quickly as possible, as changes in composition would
rapidly occur at a high temperature. Milk is usually set
for cream in shallow vessels, the depth of milk being
perhaps 8 inches ; in these vessels the milk stands for
thirty-six to forty-eight hours, till the cream has separated.
Under these conditions a large surface is exposed to the
influence of air, and a maximum amount of change takes
place ; the result is a decomposition of a part of the al-
buminoids and fats, the production of lactic acid, and
the partial curdling of the milk. The cream obtained in
this way is contaminated with curd, and contains various
strongly flavoured products of decomposition, which de-
teriorate the quality of the butter.

On Swartz's plan the milk is placed in metal pails.

120 THE CHEMISTRY OF THE FARM.

16 inches deep, and surrounded by ice. The cream rises
quickly, and can all be obtained in twelve to twenty-four
hours from the time of setting. Cream thus prepared is
perfectly sweet, and free from curd, the low temperature at
which the milk has been kept having reduced chemical
change to a minimum. It occasionally happens that milk
will not yield its cream at low^ temperatures ; this is
sometimes the case with the milk of cows several
months after calving, and especially, when receiving a
winter diet.

A third plan of separating cream is by subjecting the
milk to extremely rapid horizontal revolution in a centri-
fugal machine ; under these circumstances the fat globules
rise into the centre of the revolving mass. In Laval's
machine the new milk enters in a continuous stream, and
is immediately separated into cream and skim-milk, the
former leaving the apparatus by a pipe at the top, the
latter by another pipe from the side. The cream thus
obtained is, of course, perfectly sweet.

Cream varies considerably in composition. Good cream,
not scalded on the Devonshire plan, may contain 55 to 65
per cent, of water, and 25 to 40 per cent, of fat. Casein
and the other constituents of milk are present in small
quantity. In sweet cream the casein may be about one-
tenth of the fat ; in cream which has soured during setting
the casein forms a much larger proportion.

Skim-Milk. — Milk thoroughly skimmed in the ordinary
way will contain about 0'8 per cent, of fat ; more than this
quantity is frequently present. When ice has been used,
the percentage of fat left in the milk will be 0*3 to 0*6 ;
and when the centrifugal machine has been employed.

THE DAIRY. 121

0"2 to O'o. The two latter processes are thus the most
effective for the removal of cream. Ordinary skim-milk
will contain about as follows : — Water, 90-0 ; albuminoids,
3*7 ; fat, 0'8 ; sugar, 4*8 ; ash, 07. Its specific gravity is
generally 1*034 to 1-037. Skim-milk is a very nitrogenous
food, the albuminoid ratio being as high as 1 : 1'7.

Butter. — The object of butter-making is to bring about
the union of the fat globules which in milk and cream
have existed separate from each other. The skilled butter-
maker is not, however, satisfied with producing a solid
mass of butter-fat ; for butter to be of good quality it
must possess a certain texture and grain, and be neither
hard nor greasy ; this desired result can only be attained
by churning at a favourable temperature. If the tem-
perature of the cream is too low, the butter will be long
in coming, and will be hard in texture. If the tempe-
rature is too high the butter will come very speedily, but
the product will be greasy, destitute of grain, and de-
ficient in quantity. No temperature can be fixed as the
best at which churning should always take place. The
proportion of solid and fluid fats in the milk varies some-
Avhat with the diet of the cow^s, and this necessitates a
change in the temperature. A rather higher temperature
will be required in winter than summer ; the temperature
must also be higher for sour cream than for sweet cream.
Generally speaking, perfectly sweet cream should be placed
in the churn at 50° to 55° Fahr., and sour cream at 52°
to 60°. When sour milk is churned for butter the tempe-
rature must be about 65°. The exact temperature most
suitable for churning may be ascertained by recording
every day the temperature employed, with the length of

122 THE CHEMISTRY OF THE FARM.

time occupied in churning, and the amount and character
of the produce ; when this is done the temperature for
each day can be regulated from the experience of the
preceding working. The temperature will rise several
degrees during churning.

Churning must always be stopped as soon as the butter
comes, any over churning spoils the texture of the butter.
The butter is then separated from the buttermilk, washed
with cold water, and after standing to solidify is carefully
worked and pressed to expel all watery" matter ; over-
working in this stage will also spoil the grain, and make
the butter greasy. Butter made from perfectly sweet
cream keeps far better than butter made from sour cream,
as the latter always contains curd, a substance very prone
to change. Salt is generally added to improve the
keeping quality of butter.

First-class butter will contain about 10 per cent, of water,
and not more than 0*5 per cent, of casein, but in ordinary
butter these proportions are greatly exceeded. Of the
fatty acids in butter about 6 per cent, are soluble in
water when separated from the glycerol with which they
are combined ; this fact serves to distinguish butter from
other animal fats in which soluble fatty acids are absent.
When butter becomes rancid the glycerides of the fatty
acids are partly decomposed, and the fatty acids liberated;
the odour and flavour of rancid butter are largely due to
free butyric acid.

Bnttermilk. — The liquid remaining in the chum after
the separation of the butter from the cream has been but
little investigated ; it must vary a good deal in composi-
tion. Danish experimenters found that when churning the

THE DAIRY. 123

cream from 1001b. of new milk '07 to '20 lb. of fat was
left in the buttermilk.

Cheese. — This substance is prepared by the action of
rennet on milk. The rennet solidifies the milk by
separating the casein from solution ; the fat globules are
separated at the same time, being entangled in the curd
formed. Rennet is a watery extract prepared from the
fourth stomach of the calf; its power of coagulating milk is
apparently due to the presence of a ferment, which doubt-
less plays a similar part in the ordinary process of diges-
tion in the calf's stomach. The action of rennet is very
slow in the case of cold milk, it becomes much more
energetic as the temperature rises; at 135° Fahr. it ceases
to act. Milk becomes sour when curdled by rennet, but
the production of acid (lactic acid) is not essential to the
curdling.

The composition of cheese depends principally on that
of the milk from which it is made ; rich cheese is made
from new milk, cream being sometimes added to the milk
for the production of the richest sorts ; poorer kinds of
cheese are made from milk wholly or partially skimmed.

The temperature at which the milk is curdled is of
great importance. If the temperature is low, the curd
is very tender and the whey difficult to separate ; if, on
the other hand, the heat is too great, the curd shrinks too
much, and becomes hard and dry. A temperature from
74° to 84° is generally employed, the lower temperature
for thin cheeses, the higher (80° to 84°) for thick.

When the curd is sufficiently firm it is carefully cut in
all directions, and the whey allowed to drain off. To
facilitate the drainage of the whey the curd is often

124 THE CHEMISTRY OF THE FARM.

heated after cutting, with the view of making it shrink
and harden ; the temperature used at this point must not
exceed 100° Fahr. The drained and broken curd is next
put into a press, to remove more effectually the last
portions of whey. It is then pulverised in a mill, salted,
again passed through the mill, and is then ready for
filling into the frames. Curd when put into the frames
should contain, according to Voelcker, about 54 per cent,
of water when thin cheese is to be made, and not more
than 45 per cent, if thick cheese is manufactured. The
curd from skim milk will contain much more water than
a curd rich in butter. The frames filled with curd are sub-
jected to a gi-adually increasing pressure for several days.
The cheese is then removed from the frame and placed
in the cheese-room to ripen.

Cheese ripens best at a moderately warm temperature ;
about 70° is a suitable degree of heat. During the opera-
tion a loss of water takes place, the loss being greatest in
the case of poor cheese. If decay, or a growth of mould
occurs, a further considerable loss of weight takes place,
the casein and fat of the cheese being decomposed
by the organic life thus introduced, while carbonic acid,
ammonia, and a variety of other products are formed. It
was once believed that fat was produced during the
ripening of cheese ; this however is not the case.

A very rich cheese, as old Stilton, may contain about
20 per cent, of water, 44 per cent, of fat, and about 29
per cent, of casein. In a good Cheddar or Cheshire
cheese we should find about 33 per cent, of water, 33 per
cent, of fat, 28 per cent, of casein, and about 3 to 4 per
cent, of ash constituents, nearly half of which would be
common salt. In skim-milk cheeses the percentage of

THE DAIRY. 125

water is greater, and that of fat less. Thus a poor single
Gloucester may contain 38 per cent, of water, 22 per cent,
of fat, and 31 per cent, of casein. In skim-milk cheese
made in Denmark, from milk from which the cream has
been very completely removed by the ice system, only 4
to 5 per cent, of fat are present.

Whey. — The whey which drains from the curd in
cheese-making is a perfectly transparent liquid, containing
the sugar and albumin originally present in the milk ; it
should not contain more than a trace of butter. If, how-
ever, the curd has been roughly treated, the milk has
been rich, and the temperature high, larger quantities of
butter will be present, and the cheese suffer in conse-
quence. When whey is rich in butter it is generally
allowed to stand till the butter has risen ; the butter may
then be added to the next churning. The average com-
position of whey is shown by Voelcker's analyses to be as
follows : — Water, 93'0 ; albuminoids, 1*0 ; fat, 0'3 ; sugar
and lactic acid, 5*0 ; ash, 0'7. The albuminoid ratio is
1 : 5-2.

In all the operations of the dairy the greatest cleanliness
must be observed ; all vessels should be washed with hot
water as soon as done with, to destroy any adhering
ferment. Without such precautions no good butter or
cheese can be made.

INDEX

Acids in plants, 3
Accumulated nitrogen, 52
Adult animal, growth of, 97
Albuminoids, 61, 65

— in food, 92

— in plants, 5
Albuminoid ratio, 80
Alumina, 19

Amides, 65, 66

Ammonia absorbed by plants, 6

— in atmosphere, 12
Animal nutrition, 60
Application of manure, 34
Artificial manuring, 47
Ash consumed and voided, 111

— in animals, 65

— in food, 78

— in plants, 2
Atmosphere, 13
Autumn manuring, 35

Bacteria, uses of, 17
Bare fallow, 50

Barley, composition of, 38, 72
Beans, 72

— composition of, 38
Beech wood, composition of, 39
Beet, composition of, 39
Blood manure, 29

Bones, 29

Brewers' grains, composition of, 72

Bulk of food, 94

Buried seed, 11

Burning soil, 22

Butter, 121

— produce of, 108
Buttermilk, 122

Cakes, composition of, 72

— manure produced by, 114
Calf, composition of, 62, 63

Carbo-hydrates, 65—67
Carbonic acid, 5, 6
Carcase weights, 63
Cattle food experiments, 80 — 84
Cellulose, 2

Cereal crops, composition of, 40
Chalk, 32
Cheese, 123

Chlorides in atmosphere, 14
Chlorophyll cells, 7
Clay, 14
Cleanliness, 124
Climate, effect of, 48
Clover hay, composition of, 38, 72
Colostrum, composition of, 96
Colour of soils, 16
Colourless plants, 7
Common salt, 33
Conservation of plant food, 57
Constituents of animals, 60
— of plants, 1 — 4

Continuous cropping, 54
Coprolites, 31
Cotton cake, 72
Cream, 118
Crops, 37^i9
— distinctive characteristics of, 54

Dairy, 117—125
Deep-rooted plants, 55
Digestibility, 78
Digestible proportion of food, 80
Digestion, 68, 80—93
Drainage, action of, 18, 21

Evaporation, action of, 7, 18
Excretion, 70
Excrement from food, 113

Fallow, bare, 50
Farmyard manure, 24 — 27

INDEX.

127

Fattening animal, growth of, 100

Fatty parts of animals, 61, 65, 66

Fatty-matters in plants, 6

Feme oxide, 19

Fertility of soil, 20

Fir, composition of, 39

Flavour of food, 94

Foods, 71—94

Foods, composition of, 71

— constituents, 65

— ■ digestible part, 80
Force-producing values of food, 91
Forest, action of, 6
Forest growth, 44

Geese, food experiments, 88
Gelatinoids, 61
Germination, 10
Grains, composition of, 72

— manure produced by, 114
Gravel, 18

Green clover, composition of, 72
Green crops, 51
Green manure, 52, 53
Green part of plants, 5, 6
Ground phosphates, 30
Growth, force used in, 98
Guano, 27
Gypsum, 32

Hay crop, composition of, 4, 74
Hay, digestion of, 82
Heat-producing viUue of food, 90, 92
High-manuring, effect of, 75
Homy matter, 61
Horses, food experiments, 86
Humus, 14

Inorganic constituents, 3
Iron in soils, 19

Leaves, function of, 4—7

Leguminous crops, composition of, 42

Lime, 15, 32

Linseed-cake, 72

Losses to the land, 56—58

Luxuriance of growth, 75

Maize, composition of, 72
Llalt dust, composition of, 72

Mangels, composition of, 39, 72

Manures, 23—36

Manure, adaptation of to crops, 45

— for eei-eal crops, 40

— for leguminous crops, 43

— for meadow hay, 41

— in foods, 109, 114
Marl, 32

Meadow-grass constituents, 4, 72
Meadow hay, composition of, 38, 41,

72
Metals in plants, 3
Milk, 117

— composition of, 63, 96

— produce of, 107
Minerals in plants, 2

Natural vegetation, 23
Nitrate of ammonium, 28

— of sodium, 28
Nitric acid produced in tillage, 51
Nitrification, 17

Nitrogen consumed and voided, HI
Nitrogen in soils, 17
Non-albuminoids in food, 92
Nutrition, processes of, 64

Oats, composition of, 38, 72
Oil, effect on digestibility, 84
Oilcake, produce of manure, 114
Organic constituents, 3
Ox, composition of, 62, 63
Oxen, excrement of, 113
Oxidation in plants, 6

Pease, composition of, 72
Percentage growth of animals, 102
Perennial crops, 12
Phosphates ground, 30
Phosphoric acid, 8, 10, 19

— — in soils, 17

Pigs, composition of, 62, 63

— food experiments, 87, 105
Pine, composition of, 39
Plant development, 11, 12

— food, sources of, 13 — 22

— growth, 1—12
Potash, 8, 10

— in soils, 17

— manure, 47
Potassium salts, 33

Potatoes, composition of, 39, 72, 92

128

INDEX.

Produce of food in ^owth, 102
Proportion of nitrogenous and non-nitro-
genous ingredients, 77

Rain-water, composition of, 14
Ratio in food, albuminoid, 80 — 93
Respiration, 69

Ripeness as affecting composition, 74
Root crops, manure for, 44
Roots, function of, 7 — 10

— manure produced by, 114

— range of, 55
Rotation of crops, 47, 50 — 59

— loss during a, 57
Ruminants, experiment with, 79, 80

Sale of produce, effect of, 58

Salt, common, 9, 33

Salt, effect on digestibility, 85

Sand, 15

Seaweed as manure, 27

Season, effect of, 48, 49

Seed, depth of covering, 11

Shallow-rooted plants, 55

Sheep, composition of, 62, 63

— excrement of, 113

— food experiments, 83
Silica on plants, 9

Skim milk, 120
Soil, 14-22

— composition of, 15

— weight of, 17
Soot, 29

Special manuring, 46

Starch, effect on digestibility, 85

— composition of, 5

Storage of food in plants, 12
Straw, composition of, 72

— manure produced bv, 114
Sulphate of ammonium, 2o
Superphosphate, 30 — 32
Swedes, composition of, 39, 72

Temperature, influence on growth,

101
Tillage, action of, 20
Timber, composition of, 2

— water in, 1
Transpiration of water, 7
Turnips, composition of, 39, 72

Urine, composition of, 112

"Warmth of soils, 15

"Waste substances in drainage-water, 19

"Water in soils, 15

— influence on food, 89
Weekly results of food, 102, 105
"Weight of soil, 17

"Wheat, composition of, 38, 72
"Wheat-bran, composition of, 72
"Whey, 124

"Winter, influence of, 49
"Wool, production of, 106

— refuse, 29

— volk of, 61
"Work of growth, 98

Young animals, growth of, 95

THE END.

BRADllTTRY, AGNEW, & CO., PRINTERS, WHITEFRIARS.

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