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Indoing this, however, I have been guided by a pretty intimate knowledge of thewants of the farmer, which has induced me to enlarge on those departments of thesubject which bear more imm

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OF

AGRICULTURAL CHEMISTRY

BY

Page 190, line 11, for "gallon" read "ton."PRINTED BY R AND R CLARK,EDINBURGH

Transcriber's note: Many of thetables needed to be split to fitspace constraints

The object of the present work is to offer

to the farmer a concise outline of thegeneral principles of AgriculturalChemistry It has no pretensions to beconsidered a complete treatise on thesubject On the contrary, its aim is strictlyelementary, and with this view I haveendeavoured, as far as possible, to avoidunnecessary technicalities so as to make itintelligible to those who are unacquaintedwith the details of chemical science,although I have not hesitated to discusssuch points as appeared essential to theproper understanding of any particularsubject

The rapid progress of agriculturalchemistry, and the numerous researchesprosecuted under the auspices ofagricultural societies and privateexperimenters in this and other countries,render it by no means an easy task to make

a proper selection from the mass of factswhich is being daily accumulated Indoing this, however, I have been guided

by a pretty intimate knowledge of thewants of the farmer, which has induced me

to enlarge on those departments of thesubject which bear more immediately onthe every-day practice of agriculture; andfor this reason the composition andproperties of soils, the nature of manures,and the principles by which theirapplication ought to be governed, havebeen somewhat minutely treated

In all cases numerical details have beengiven as fully as is consistent with thelimits of the work; and it may be right tostate that a considerable number of theanalyses contained in it have been made in

my own laboratory, and that even when Ihave preferred to quote the results of otherchemists, they have not unfrequently beenconfirmed by my own experiments

University of Glasgow,

1st November 1860.

Introduction

CHAPTER I

The Organic Constituents of Plants

Carbon Carbonic Acid Hydrogen .Nitrogen Nitric Acid Ammonia .Oxygen Sources whence obtained .The Atmosphere The Soil Source ofthe Inorganic Constituents of Plants .Manner in which the Constituents of Plants

are absorbed

CHAPTER II

The Proximate Constituents of Plants

The Saccharine and AmylaceousConstituents Cellulose IncrustingMatter Starch Lichen Starch .Inuline Gum Dextrine Sugar .Mucilage Pectine and Pectic Acid .Oily or Fatty Matters Margaric, Stearic,and Oleic Acids Wax Nitrogenous orAlbuminous Constituents of Plants andAnimals Albumen Fibrine Casein Diastase

CHAPTER III.

The Changes which take place in the Food

of Plants during their Growth

Changes occurring during Germination .Changes during the After-Growth of thePlant Decomposition of Carbonic Acid Decomposition of Water .Decomposition of Ammonia .Decomposition of Nitric Acid

CHAPTER IV

The Inorganic Constituents of Plants

The Amount of Inorganic Matters inDifferent Plants The Relative

Proportions of Ash in the Different Parts

of Plants Influence of the Nature of theSoil on the Proportion of Mineral Matters

in the Plant The Composition of theAshes of Plants Classification ofDifferent Plants

Physical Characters Relation to Heatand Moisture The Subsoil .Classification of Soils

CHAPTER VII

The General Principles of Manuring

Fundamental Principles upon which

Manures are applied Special and

General Manures Importance of this

distinction Views regarding the Theory

of Manures Remarks on SpecialManures Action of Manures on theChemical and Physical Properties of aSoil Remarks on the Application ofManures

Farm-yard Manure Composition of Management of Dung-Heaps Box-feeding Fermentation and application ofManure Liquid Manure Compositionand application of Sewage Manure .Its composition and application

various Sea-Weeds Leaves Peat

of Adulteration of Application of .Pigeons' Dung Urate and SulphatedUrine Night-Soil and Poudrette Hair,Skin, Horn, Wool, etc Blood Fish

"Fish-Guano"—Bones

CHAPTER XI

The Composition and Properties ofMineral Manures.

Mineral Manures Sulphate and Muriate

of Ammonia Sulphomuriate ofAmmonia Ammoniacal Liquor .Nitrates of Potash and Soda Muriateand Sulphate of Potash Chloride ofSodium, or Common Salt Carbonates ofPotash and Soda Silicates of Potash andSoda Sulphate of Magnesia .Phosphate of Lime Bone-ash .Coprolites Apatite Sombrero Guano Superphosphates and Dissolved Bones Biphosphate of Lime or SolublePhosphates Phospho-Peruvian Guano Lime Chalk Marl Application andAction of Lime on Soils Sulphate of

Lime or Gypsum

CHAPTER XII

The Valuation of Manures

The Principle on which Manures arevalued Its application to differentsimple and complex Manures Method

of Calculation General Remarks

CHAPTER XIII

The Rotation of Crops

Its necessity explained Quantity ofMineral Matters in the produce of an Acre

of Different Crops The Theory ofRotation

CHAPTER XIV

The Feeding of Farm Stock

The Principles of Feeding TheComposition of different Animals indifferent stages of Fattening TheComposition of the Food of Animals .Milk The Principal Varieties of CattleFood General Observations on Feeding

AGRICULTURAL CHEMISTRY.

That the phenomena of vegetation aredependent on certain chemical changesoccurring in the plant, by which thevarious elements of its food areelaborated and converted into vegetablematter, was very early recognised bychemists; and long before the correctprinciples of that science wereestablished, Van Helmont maintained thatplants derived their nourishment fromwater, while Sir Kenelm Digby, Hook,Bradley, and others, attributed an equallyexclusive influence to air, and enlarged onthe practical importance of theconclusions to be deduced from their

views These opinions, which were littlebetter than hypotheses, and founded onvery imperfect chemical data, arementioned by Jethro Tull, the father ofmodern agriculture, only to deny theiraccuracy; and he contended that the plantsabsorb and digest the finer particles of theearth, and attributed the success of theparticular system of husbandry headvocated to the comminution of the soil,

by which a larger number of its particlesare rendered sufficiently small to permittheir ready absorption by the roots.Popular opinion at that time was in favour

of the mechanical rather than the chemicalexplanation of agricultural facts, andTull's work had the effect of confirmingthis opinion, and turning attention awayfrom the application of chemistry to

agriculture Indeed, no good results couldhave followed its study at that time, forchemistry, especially in those departmentsbearing more immediately on agriculture,was much too imperfect, and it was onlytowards the close of the last century, whenLavoisier established its true principles,that it became possible to pursue it withany prospect of success.

Very soon after Lavoisier's system wasmade known, Lord Dundonald publishedhis "Treatise on the Intimate Connexionbetween Chemistry and Agriculture," inwhich the important bearings of the recentchemical discoveries on the practice ofagriculture were brought prominentlyunder the notice of the farmer, and almost

at the same time De Saussure commenced

those remarkable researches, whichextended over a long series of years, andlaid the foundation of almost all ouraccurate knowledge of the chemistry ofvegetation Saussure traced with singularcare and accuracy the whole phenomena

of the life of plants, and indicated themode in which the facts he establishedmight be taken advantage of in improvingthe cultivation of the soil But neither hisresearches, nor Lord Dundonald's moredirect appeal to the farmer, excited theattention they deserved, or produced anyimmediate effect on the progress ofagriculture It was not till the year 1812that the interest of practical men wasfairly awakened by a course of lecturesgiven by Sir Humphrey Davy, at theinstance of Sir John Sinclair, who was at

that time president of the Board ofAgriculture In these lectures, written withall the clearness and precision whichcharacterised their author's style, theresults of De Saussure's experiments werefor the first time presented to the farmer in

a form in which they could be easilyunderstood by him, the conclusions towhich they led were distinctly indicated,and a number of useful practicalsuggestions made, many of which havebeen adopted into every-day practice, andbecome so thoroughly incorporated with

it, that their scientific origin has beenaltogether forgotten A lively interest wasexcited by the publication of Davy's work,but it soon died out, and the subject lay inalmost complete abeyance for aconsiderable number of years Nor could

any other result be well expected, for atthat time agriculture was not ripe forchemistry, nor chemistry ripe foragriculture The necessities of a rapidlyincreasing population had not yet begun tocompel the farmer to use every meansadapted to increase the amount ofproduction to its utmost limit; and thoughthe fundamental principles of chemistryhad been established, its details,especially in that department which treats

of the constituents of plants and animals,were very imperfectly known It is notsurprising, therefore, that matters shouldhave remained almost unchanged for thecomparatively long period of nearly thirtyyears Indeed, with the exception of theinvestigation of soils by Schübler, andsome other inquiries of minor importance,

and which, in this country at least, excited

no attention on the part of the agriculturist,nothing was done until the year 1840,when Liebig published his treatise on

Chemistry, in its application to Agriculture and Physiology.

Saussure's researches formed the maingroundwork of Liebig's treatise, as theyhad before done for Davy's; but theprogress of science had supplied manynew facts which confirmed the opinions ofthe older chemists in most respects, andenabled Liebig to generalise with greaterconfidence, and illustrate more fully theprinciples upon which chemistry ought to

be applied to agriculture Few works haveever produced a more profoundimpression Written in a clear and forcible

style, dealing with scientific truths in abold and original manner, and producing astrong impression, as well by itsearnestness as by the importance of itsconclusions, it was received by theagricultural public with the full convictionthat the application of its principles was

to be immediately followed by theproduction of immensely increased crops,and by a rapid advance in every branch ofpractical agriculture The disappointment

of these extravagant expectations, which

chemists themselves foresaw, and for

which they vainly attempted to prepare theagriculturist, was followed by an equallyrapid reaction; and those who hadembraced Liebig's views, and lauded them

as the commencement of a new era, butwho had absurdly expected an

instantaneous effect, changed theiropinion, and contemned, as strongly asthey had before supported, the application

of chemistry to agriculture

That this effect should have beenproduced is not unnatural; for practicalmen, having at that time little or noknowledge of chemistry, were necessarilyunable to estimate its true position inrelation to agriculture, and forgetting thatthis department of science was still in itsearly youth, and burthened with all thefaults and errors of youth, they treated it as

if it were already perfect in all its parts.Neither could they distinguish between thefully demonstrated scientific truths, andthe uncertain, though probable conclusionsdeduced from them; and when the latter, as

occasionally happened, proved to be atvariance with practice, it is not surprising:that this should have produced a feeling ofdistrust on the part of persons incapable,from an imperfect, and still oftener from

no knowledge of science, of drawing theline of demarcation, which Liebigfrequently omitted to do, between thepositive fact and the hypotheticalinference, which, however probable, is,after all, merely a suggestion requiring to

be substantiated by experiment Thisomission, which the scientific reader cansupply for himself, becomes a source ofserious misapprehension in a workaddressed to persons unacquainted withscience, who adopt indiscriminately boththe facts and the hypotheses of the author.And this is no doubt the cause of the vary

different estimation in which the work ofthe Giessen Professor was held byscientific and practical men.

Liebig's treatise was followed, in the year

1844, by the publication of Boussingault's

Economic Rurale, a work winch excited

at the time infinitely less interest thanLiebig's, although it is really quite asimportant a contribution to scientificagriculture It is distinguished by enteringmore fully into the special details of theapplication of chemistry to agriculture,and contains the results of the author'snumerous searches both in the laboratoryand the field Boussingault possesses thequalification, at present somewhat rare, ofcombining a thorough knowledge ofpractical agriculture with extended

scientific attainments; and hisinvestigations, which have been madewith direct reference to practice, and theirresults tested in the field, are the largestand most valuable contribution to theexact data of scientific agriculture whichhas yet been made public.

The year 1844 was also distinguished bythe foundation of the AgriculturalChemistry Association of Scotland, anevent of no small importance in the history

of scientific agriculture That associationwas instituted through the exertions of asmall number of practical farmers, for thepurpose of pursuing investigations inagricultural chemistry, and affording to itsmembers assistance in all mattersconnected with the cultivation of the soil,

and has formed the model of similarestablishments in London, Dublin, andBelfast, as well as in Germany; and it ispeculiarly creditable to the intelligenceand energy of the practical farmers ofScotland, that with them commenced amovement, which has already foundimitators in so many quarters, andconferred such great benefits onagriculture Within the last ten or twelveyears, and mainly owing to theestablishment of agricultural laboratories,great progress has been made inaccumulating facts on which to found anaccurate knowledge of the principles ofagricultural chemistry, and the number ofchemists who have devoted themselves tothis subject has considerably increased,though still greatly less than its exigencies

Notwithstanding all that has recently beendone, it must not be forgotten that we havescarcely advanced beyond the threshold,and that it is only by numerous andfrequently repeated experiments that it ispossible to arrive at satisfactory results.Agricultural inquiries are liable topeculiar fallacies due to the perturbinginfluence of climate, season, and manyother causes, the individual effects ofwhich can only be eliminated withdifficulty, and much error has beenintroduced, by hastily generalising fromsingle experiments, in place of awaitingthe results of repeated trials Hence it isthat the progress of scientific agriculturemust necessarily be slow and gradual, and

is not likely to be marked by any great orstartling discoveries Now that therelations of science to practice are betterunderstood, the extravagant expectations

at one time entertained have beenabandoned, and, as a necessaryconsequence, the interest in agriculturalchemistry has again increased, and theconviction daily gains ground that no onewho wishes to farm with success, canafford to be without some knowledge ofthe scientific principles of his art

CHAPTER I.

THE ORGANIC

CONSTITUENTS OF

PLANTS.

When the water naturally existing in plants

is expelled by exposure to the air or agentle heat, the residual dry matter isfound to be composed of a considerablenumber of different substances, whichhave been divided into two great classes,called the organic and the inorganic, ormineral constituents of plants The formerare readily combustible, and on the

application of heat, catch fire, and areentirely consumed, leaving the inorganicmatters in the form of a white residuum orash All plants contain both classes ofsubstances; and though their relativeproportions vary within very wide limits,the former always greatly exceed thelatter, which in many cases form only avery minute proportion of the wholeweight of the plant Owing to the greatpreponderance of the organic orcombustible matters, it was at one timebelieved that the inorganic substancesformed no part of the true structure ofplants, and consisted only of a smallportion of the mineral matters of the soil,which had been absorbed along with theirorganic food; but this opinion, whichprobably was never universally

entertained, is now entirely abandoned,and it is no longer doubted that bothclasses of substances are equally essential

to their existence

Although they form so large a proportion

of the plant, its organic constituents arecomposed of no more than four elements,viz.:—