Elementary lessons in the science of agricultural practice

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Preface

THis elementary work has been prepared to meet the requirements of two distinct classes of students. For those who have some knowledge of agricultural practice it will probably act as a familiar introduction to the instruction given in various Manuals of agricultural science. On the other hand, it is hoped that the student who has little or no knowledge of farm practice will find it a convenient sequel to such works. The scope of this elementary book has been limited to a familiar outline of the more important conditions which influence the growth of farm crops ; hence it does not extend to the utilisation of these crops by the aid of animal life.

Lonpon, Jovember 1881.

v

ELEMENTARY LESSONS

IN THE

SCIENCE OF AGRICULTURAL PRACTICE.

Chapter I

THERE is a very great difference of opinion as to what is meant by Agricultural Science. It isa term very frequently used to express very different ideas, according to the knowledge and judgment of the person using it; but it is manifestly desirable that there should be a clear recognition of its true meaning, Agricultural Science may be fairly described as “Scientific truths taught by the Practice of Agriculture.” It isa definition which will probably lead some to remark, “I thought that Agricultural Science was intended to teach me how to farm, but the order is here reversed, for this makes the Practice of the Farm teach me the Science of Agriculture.” Such a comment would be perfectly just, and the title which has been chosen for this book is intended to prevent—as far as may be pos- Z

2 THE SCIENCE OF [omar. 1.

sible—any misapprehension as to the general character of Agricultural Science. As soon as we accept this definition of Agricultural Science, we are thereby guided into a safe course for obtaining sound and reliable information on the subject. The laws of Agricultural Science will be most accurately learnt — when they are deduced from the practice of farming, and from a careful observation of the conditions which control the production of our crops. When this truth is cordially acknowledged, we see men of science learning from farmers the science of their practice, and in doing so they communicate to the cultivators of the soil much useful information, which will lead to improvements in the application of science to farm practice. The exchanges of thought benefit both, and’ as a natural consequence both groups have some new light thrown upon the views previously held, and in each case a thirst for a fuller and more perfect knowledge of the matter will be .- | established.

This result is most perfectly attamed when you have the two characters blended in one and the same individual, such as when a farmer has been a student of science, or when a man well educated in science has been engaged in the cultivation of the soil. It is this combined knowledge of science and of practice which perfects the judgment, and renders the opinions formed more complete and more accu- — rate. The terms, Scientific Agriculture, Agricultural Science, and Agricultural Chemistry, are very often used as if they had exactly the same meaning. Other

CHAP. I.] AGRICULTURAL PRACTICE. 3 persons fail to see any distinction between Agricultural Science, and the study of chemistry, botany, geology, and physiology ; but these difficulties really arise from an imperfect knowledge of the matters spoken of. If, however, the definition already given of Agricultural Science be accepted, there will then be less danger of confusing terms which have such distinct and different meanings. The sciences of chemistry, botany, geology, and physiology, etc., rightly used, are each and all of them of immense value and importance to the farmer. They are, in fact, a series of detached assistant agencies, which require to be brought into concerted action ; and the only means by which this can be accomplished for the advantage of the farmer is by the aid of Agricultural Science. ‘This condition of things is not peculiar to agriculture ; it attaches to every case in which science is made use of for improving any of our manufacturing industries. All hold one common relationship, but they vary considerably in the extent to which such co-operation extends ; and there is no _ reason whatever why the business of farming should be separated from the series. |

The study of pure science is valuable, amongst other things, in enabling a man to inform himself as to the character and composition of the materials he has to deal with. It matters little what the material may be which he has to work upon—it may be either an animal or vegetable product, or a mineral— if he knows its general nature and specialties of character, then he can deal with it with greater success.

4 (THE SCIENCE OF [oHAP. 1

The manufacturer studies that branch, or those branches, of science, which have reference to the material he intends dealing with; and he does so in order that he may the more successfully learn the practical details of his business. The study of pure science is as a lamp which aids him to see the why and the wherefore of the operations taking place around him, but he has still to gather the practical knowledge or experience of the business or manufacture, in order that he may work in the light so given. For the interests of farming we want this practical work to proceed under a clearer and brighter light. The several branches of science are ready to contribute their help. Chemistry has done, and will still do, much to throw light upon this work ; but it comes, as it were, with its own special tint. Other branches of science are capable of doing similar good service, but when any one is used alone it throws a tinted light. It is when they all contribute to the work that we get the clear and perfect light we need. We have an illustration which happily explains these facts. White light consists of coloured lights which ‘can be separated, giving the varied colours of the rainbow ; but when these are blended again we lose these distinctive tints, and reproduce a clear, bright, and colourless light. So also, if we bring a wellbalanced and tolerably complete knowledge of science to bear upon agricultural practice, we lose the tints — given by different sections of science, and we get a brighter and purer light to aid us in our labours.

Chap. I. ] Agricultural Practice. 5

Happily for the progress of Agricultural Science, we have a large number of farmers in this country who have received a good training in science, and they are from day to day gathering-in fresh truths from their experience in agriculture, learning valuable lessons from their successes and from their failures, steadily accumulating evidence from Nature’s own mouth, and thereby enabling some more complete and definite character to be given to Agricultural Science. Thus, whilst we suggest that a study of pure science prepares the farmer for observing results with greater accuracy, and for tracing those results to their proper causes, we should be guilty of a great oversight if we did not recognise the fact, that the rich stores of ‘knowledge which we find in the minds of experienced farmers, contain many a precious grain of truth, although it may not have been winnowed as clean as if they had had the opportunity of acquiring some knowledge of the sciences. It is a duty to point out the advantages of a study of science as preparing any one for understanding more fully the materials he has to deal with, but it is also incumbent upon us to remember that many have not had this preparation, and yet have struggled on against the stream, gathering-in their contributions to the science of agriculture. These may want more or less winnowing, but those who look upon Agricultural Science as it has been herein defined,—as “ Scientific truths taught by the Practice of Agriculture,’—will see that the experience of practical farmers is the great storehouse of Agricultural Science, and

6 THE SCIENCE OF [CHAP. II.

that, instead of such science being in any way opposed to practice, it is its very essence, its life, the spirit by which it is animated.

CHAPTER IL

THE cultivation of the soil is now regarded by all intelligent men as a manufacturing business of the highest importance to the welfare of this country. It is generally carried out in that rough and ready manner which distinguishes the practice of those who adopt a certain course of procedure, because it will probably lead to successful results. The experience of the farmer is a very valuable guide in the attainment of such results. It should be distinctly recognised as absolutely essential for those who would succeed in the cultivation of the soil, and a possession of this knowledge should be accepted as a necessity of the case. ‘There must be no doubt whatever of the immense value of sound practical knowledge of farm management, for it stands in the same relation to the cultivation of the soil as the rudder does to the ship. An absence of either of these, simply indicates a drifting to destruction, rather than the attamment of success. In both cases the issue depends upon a series of uncontrolled influences, and the probabilities in both instances are in favour of failure and disappointed hopes. A ship with a rudder to guide it may meet with misfortune and

CHAP. II. ] AGRICULTURAL PRACTICE. 7 danger ; but the value of the rudder is admitted because it so generally prevents loss, and enables the voyage to be terminated with feelings of satisfaction ; and a knowledge of practical farming is equally important. Whatever may be our views of the great value of Agricultural Science, we ought always te remember that the only foundation on which it can rest is a sound and practical knowledge of farming operations.

Whilst we thus recognise farm experience as the rudder which controls our course, we may also regard Agricultural Science as the mariner’s compass, which indicates to the experienced sailor the nearest and best line for his ship to take. However much we may value the rudder, we know how great are the advantages arising from the supplemental help of the compass. Nor must we forget that neither are of value to any but those who are accustomed to their use. Both, however, become of priceless value when skilfully used.

Thus, in approaching a consideration of Agricultural Science, we must clearly recognise the fact that, rightly and judiciously employed, it- may be made a valuable supplemental help to those who have a sound and practical knowledge of farm operations. It is as foolish to reject the aid of Agricultural Science as it would be to cast the mariner’s compass from the ship; and, on the other hand, any doubt as to the necessity for farm experience is as devoid of reason as an indifference respecting the need of a rudder. Each of these departments

8 | THE SCIENCE OF [OHAP. IL of agricultural knowledge is of immense value—they are not opponents, but joint contributors to success. The prudent man will rightly use both of them, and consistently seek to become more and more fully acquainted with each.

This acquirement of a knowledge of Agricultural Science necessarily claims our attentive thought and steady perseverance, but considerable advance may be made without any undue demands being made on either—especially when the subject is brought under consideration stripped of all needless technicalities. In these Elementary Lessons some of the foundation-stones of the structure will be exposed to view, with a desire to encourage the reader to seek out others which underlie many of the successful practices of the farmer; so that he also may contribute to the fuller knowledge of the subject. It may be readily admitted that our knowledge of the principles of agriculture is very imperfect; and that there is an abundant opportunity for those who are acquainted with the practice of agriculture to discover some of the principles upon which such practice is based. If we accept the experience of the farmer as a rich store of facts from which, by the light of science, we may discover an explanation of the results which have been observed, then, and then only, shall we be adopting a safe and prudent course—especially during the early period of research. We must for a time seek after facts, and investigate the conditions under which these have arisen, rather than look out for such facts as will dovetail in with any precon-

CHAP. II. ] AGRICULTURAL PRACTICE. 9 ceived ideas of Agricultural Science. Conscious of the want of more truth to guide us, we shall follow the safest course if for a time we gather out the jewels which have already been brought within our reach by successful practice, and thus labour zealously in the attainment of a more complete knowledge of the subject. We must thoroughly realise the fact that Agricultural Science is really the Science of Agricultural Practice, or, in other words, that it is those lessons of scientific truth which we may learn from the experience of the practical farmer.

But in order that we may be able to learn these lessons, we must first be content to acquaint ourselves with some of the conditions and circumstances which influence the operations of the farm. The soil naturally presents itself to our notice as being worthy of our study. We have spoken of the cultivation of the soil as a manufacturing business, and thus we have the soil as the raw material, which has to be converted into those marketable products which are most desirable for a farmer to sell, Other manufacturers use the raw materials which best meet their requirements, but it is from the soil that the farmer has to produce those varying forms of animal and vegetable food which it is to his interest to manufacture. It is therefore clearly desirable that those who are to support themselves by the cultivation of the soil, should have a very complete knowledge of the character of the soil which they have to cultivate. In fact, we may say that it is not only desirable, but actually necessary, if the cultivator

10 ' THE SCIENCE OF [CHAP. Il.

wishes to draw from that soil the largest produce of the greatest value, and at the least cost in cash and material.

The soil is very commonly regarded simply as earthy matter, which is devoid of all interest except as regards the plants which grow upon it.. But this is far from being the fact, for as we become more intimately acquainted with our soils we see evidences of character which well-nigh constitute them living realities. We find points of character which indicate powers approaching very closely to tempers, wills, and dispositions, which the farmer is bound to consider, and which he neglects at his peril. Many a soil is said to have “a will of its own,” because if its peculiarities of temper be disregarded much of our labour is expended uselessly. - Much of the farmer’s success turns upon his familiar acquaintance with those points of character which is commonly known as the temper of the soil, and yet how few stop to inquire as to the causes of these variations. But when these variations in character are traced out, and when a person thereby becomes more familiar with them, it appears almost to invest our soil with new attributes of life. Hence we have become accustomed to speak of soils as being hungry, or sick, or grateful, and as obstinate, kindly, and tender, and so on. The plain fact is, the more we know of the soil the more interesting it becomes, until it causes a feeling of surprise that any one can look upon the soil with the indifference which arises from an entire ignorance of its character.

Chap. Iii.] Agricultural Practice. 11

But, besides all this, the soil boasts of a history extending over long periods of time, during which it has undergone changes of the greatest importance ; in fact, its history gives us a series of incidents of most thrilling interest, and contributes greatly to surround the soil with associations which not only give to the reflective mind subjects worthy of careful consideration, but they indicate to the farmer how he may make that soil a source of greater profit to himself.

Chapter III

AS soon as attention is directed to a consideration of the nature and character of the soil, the inquiry naturally arises:—How were these soils formed, and whence came they? With one exception, our soils have been formed by the decay of rocks. It is a matter of common observation that the stones of old buildings do not look as smooth as those which have been more recently built. We sometimes see modern stonework losing its sharp edges by becoming crumbled into dust; but it is much more evident on looking at the stonework of old buildings. Thus we have instances of even the hardest stones undergoing decay on the surface, and becoming in this way changed from hard rock into a soft or a gritty powder. ‘This change on the surface of this stonework is very similar in character to the decay of our rocks, whereby they are made to yield

12 * THE SCIENCE OF [CHAP. III, portions of their surface in that, more or less, finely broken condition which we know as the soil.

The wearing down of the stonework of our buildings fairly represents the mode in which rocks decay, and yield that earthy matter which we use for the purposes of cultivation; but in the one case a very small quantity of soil is produced, and in the other it has been accomplished to an exceedingly large extent. Through long geological periods, which we fail to reduce to figures with any pretension to accuracy, this decay of rocky surface has been steadily and persistently taking place, until at length we have an abundance of this earthy matter distributed throughout the world, and in quantity more than sufficient for the wants of mankind.

A study of geology teaches us that at one period —far, far remote in the world’s history—the surface of the earth consisted of rocks which are now known as the primitive rocks, or, plainly speaking, the first rocks. We have large masses of these rocks still remaining, so that we can form a very accurate opinion of their nature and character. But a period arrived when portions of these rocks became decayed, as rocks decay now, and then we had earthy matter formed from these rocks, yielding the first soil upon this world’s surface. From that time we have had a series of changes upon the earth’s surface, which the study of geology partially unfolds to our view; but we have one great fact which it is necessary for the student of Agricultural Science to remember. That first soil which has been already referred to has

CHAP, III. ] AGRICULTURAL PRACTICE, 13 undergone many changes; it has been formed into rocks, and again turned into soil, by their decay ; changed again into rock, and again into soil, and this has been taking place over and over again, as our various geological formations were being built up. It is as if some materials of a building had been repeatedly used in the reconstruction of some more recent portion, and that these had been again partially employed in a similar manner. The earliest soil produced from the primitive rocks in like manner has become rock and then soil, and again rock and then soil, very many times. In the periods during which it was existing as soil, it may have been intermingled with the soils produced from other primitive rocks, but of a somewhat different composition, and thus its character may have been changed, The changes which have been taking place have been a series of reconstructions of the same original earthy matter, and these have often been modified in character by the influences of animal and vegetable life. Thus the soil of the field has an antiquity of no ordinary character, and it has probably taken part in many of the great changes on the earth’s surface. This is beyond doubt a matter of very deep interest, but there is one practical issue which we must not overlook—viz. that as these reconstructions have been taking place in the manner referred to, we ought to find in the primitive rocks materials similar to those which we have in the soils of our fields. These primitive rocks were the first grand store of solid mineral matter,

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the magazine from which all the supplies were drawn, and the various rocks which were found at latter periods of time were little more than reconstructions of the original materials of the primitive rocks. Asa matter of fact we do find in the primitive rocks just those mineral matters which now exist in our soils.

These primitive rocks practically consist of three tolerably distinct groups, which are known as Granite, Syenite, and Trap, and their composition is as follows :—

ANALYSES OF PRIMITIVE ROCKS.

Granite. _ Trap. Syenite.

Siliga ra 4. ssract Gh 72 43° | 59°8 Alumina. ‘ ‘ 16. ee | 16°8 Ferrous Oxide . 125 15°3 | is Lime : r 4 1°5 Oeil eae | Magnesia : : z) 271 2°6 Potash . ; : 6° 13 6°6 Soda : 5 E 2°5 3°9 iL Phosphoric Acid, Sul- ) phur, Manganese traces, traces. | traces. Moisture. . . * 1:3 1-4 100° 100° | 100:

a

If we notice the minerals each of these contains, and . trace out their composition as shown by chemical

CHAP. III.] AGRICULTURAL PRACTICE. 15

_ analyses, we find these primitive rocks differ greatly in the materials each would yield upon decay. Thus the original earthy matter varied very greatly in composition and character; and according to the proportions in which these happened to become mixed, so was the character of the reconstructed rocks modified. So also in the soils which were produced by their decay equally marked variations were to be found. In this way we have immense variations in the character and composition of the soils now existing on the world’s surface. :

It is desirable, as we proceed, to notice how the decay of rocks into earthy matter is accomplished. We have seen that ordinary stone buildings bear signs of the same decay which took place in the early period of the world’s history on the first rocks on the earth’s surface, and which continues to take place at the present time. The agencies are very simple, and easily understood. It is, moreover, exceedingly important that these agencies should be familiarly known to the student of Agricultural Science, because they are valuable friends to the cultivator of the soil, and it is always desirable to be acquainted with our friendly helpers.

Those who have watched farm work have probably been often struck with the bright polished surface of the mould-board of an iron plough after it has been used on some of our soils, and especially on sandy soils. When the work is completed, and the plough is allowed to stand out in the field, the bright polished surface soon becomes covered with rust, This rust

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is caused by something in the air, which attacks the — iron. Chemists are able to trace out what it is in the air which does this, and they find that it is a body which is commonly known to us by the name of oxygen, which is really at the bottom of the mischief. We also know that this oxygen has a companion in the air which also helps on the work, and it bears the name of carbonic acid. These two gases—for they are as colourless and transparent as air—are found to help each other very much ; and they not only attack metals, such as the bright mould-board we have referred to, but they attack rocks, however hard and tough they may be. If you rub the rusty surface of the mould-board, you can remove a powder, and this shows that the hard metal can be reduced to a soft powder. That powder contains iron, which has been separated from the iron mould-board by these agencies, for even its great strength had failed to resist their attack. If that iron had been beaten or crushed to the greatest possible extent, it could not have been as completely powdered as it was done by these two gases, without any noise, and almost without observation. Thus, although we cannot see these two bodies, we easily learn that they are very powerful, and it will cause no surprise when we say that they are equally powerful in breaking down rocks, even when those rocks are as hard as granite.

CHAR. Iv.] AGRICULTURAL PRACTICE. 17

Chapter IV

THe changes of temperature and the action of water are another pair of agents which work together in helping to convert rocks into soil. As we have already noticed, the two gases in the air helped forward the breaking down of metal and rock into fine powder, and the work was made more effective by their united action. It is just the same with these additional agents; by working together these also become increasingly powerful. It may be well just to notice one way in which a hard rock may be attacked, and how the surface may be removed and crushed to powder.

We will take the hardest granite rock, and see how they attack it. It happens that the granite, with all its strength, has two bodies in it, which are really prepared to act as traitors in the camp, and these bodies are iron and potash. Both of these substances are commonly known to us all, and we have therefore a certain familiar acquaintance with them. ‘The iron in the granite is soon found to enter into alliance with some of the oxygen and carbonic acid of the atmosphere, just as happened in the case of the iron mould-board of the plough, and after a time we see on the face of the granite a rusty mark. This rusty mark has been caused by the rain-water removing the rust formed on the face of the granite. In fact we have here an exact repeti-

1.0

18 THE SCIENCE OF [CHAP. IV.

tion of the iron being reduced into a very fine powder, only it is the granite rock which has given it up, instead of the iron mould-board.

After this has been going on for many many years we find little holes in the granite. The constant action of these agents is like so many miners driving a number of adits into a rock, and as they send away what they dig, they leave passages open in the rock, So also these atmospheric miners make a series of very fine passages in the rock, because they have been removing some of the iron and potash from it, and thereby there is room for water to penetrate and fill these little passages. Whenever a frost comes on, the water in these passages becomes hard, and in doing so it also tries to become bigger. ‘The same sort of thing takes place in the water pipes of our houses when the water becomes frozen. If the pipes are stronger than the force exerted by the freezing water, no damage arises; but if the pipes are not strong enough, then the swelling of the water as it becomes formed into ice bursts the pipes, and when the thaw comes great inconvenience is caused in the house by water coming from the pipes where it is not wanted. It is very similar when the water soaks into a rock and then becomes frozen—sooner or later it bursts off the surface, and reduces it toa broken condition.

The continued attack does not stop even then, for any portions of stone which may thus be thrown off are again worked at just as we have noticed in the case of the rock. These atmospheric influences

CHAP. IV.] AGRICULTURAL PRACTICE. 19 are like a well-trained company of sappers and miners; they bore out the passages and blow up the parts thus mined, and finally reduce the strongest material to small particles. But they differ in one respect, for their work is constant ; they cease not from weariness, nor stay for refreshment, but day and night, from century to century, they are either driving passages into rocks, or blowing portions of the rock into atoms,

We have spoken of the hard fight which takes place in the granite rock, and the idea may arise that this only happens upon a very small scale ; but it will be found that the extent of work thus accomplished, when the world’s surface consisted only of the primitive rocks, was something so immeasurably great, that it is beyond our power to understand its extent. The progress of the work is, of course, very much more rapid upon softer rocks of more recent date. We see it taking place around us, and we find that rocks which are exposed to the air, as they gradually get covered with soil, so they are more or less protected from the air, and consequently the reduction into soil is held under control. Hence it is that some rocks are so largely covered by soil, and yet beneath that soil we find the hard rock remaining.

In this, as in all the operations of nature, we have some useful purpose to be secured, and when that object has been gained we find no wasteful exercise of power. The reduction of rocks into soil has been necessary, in order that the surface of the earth may be prepared for its varied duties, and of