Presented to Che Hibrary of the 5 University of Toronto by Mrs C. Dorothy Burns Tete § = 4 Seles AGRICULTURE | ILLIAM SOMERVILLE, M.A., D.Sc. - _ Lonpon ent Pies agee so se es eae PR awe 3 ee ty ee Ee tera Bt i= od 1 HOME NON UNIVERSITY LIBRARY OF | MODERN KNOWLEDGE Editors: HERBERT FISHER, M.A., F.B.A. Pro¥. GILBERT MURRAY, D.LITT., LL.D., F.B.A. ProF. J. ARTHUR THOMSON, M.A. PROF. WILLIAM T. BREWSTER, M.A, (Columbia University, U.S.A.) ”~ . 3 - _ NEW YORK HENRY HOLT AND COMPANY S {ty : Mf] AGRICULTURE | BY WILLIAM SOMERVILLE D.SC., OXFORD AND DURHAM ; D.CE&C., MUNICH ; B.SC., EDINBURGH ; SIBTHORPIAN PROFESSOR OF RURAL ECONOMY, AND FELLOW OF ST. JOHN’S COLLEGE, IN THE UNIVERSITY OF OXFORD. LONDON WILLIAMS AND NORGATE ITED Oar Giga s < a oO. & Pri: ' Edt; Mor = tis ete eerie Aes, creed, PREFACE THE object of this volume is to discuss the fundamental principles underlying the practice of agriculture. It is, in the main, an intro- duction to crops and cropping, and contains the sort of information that a farmer may be expected to possess who aims at cultivating his fields and manuring his crops intelligently. The special requirements of the readers for whom the series is intended have constantly been borne in mind; and it is hoped that, supplemented by the selection of the works mentioned at the end, the little volume may be useful for those who have to gather their knowledge without much aid from laboratories and lecture rooms. W. S. aia boa, pseieeieic oan bautpie- to Viil CONTENTS Toe Formarion oF Soin THE PROPERTIES OF SOIL THE Marin Typss or Soiz . AMELIORATION AND IMPROVEMENT OF LAND. THE PRINCIPLES OF ManuRING, THE NITRO- GENOUS MANURBRES PuHospPHatic, NITROGENOUS-PHOSPHATIC, AND Porassic MANURES . THE Errectivs Uss or ARTIFICIAL MANURES FARMYARD MANURE ROTATION OF CROPS SEED BIBLIOGRAPHY INDEX . Vil 161 173 188 219 252 254 wt 4 et ae getter . aN BIOGEN, mea ; 2. ae Sows 2 ee " Ua — g AGRICULTURE CHAPTER I THE FORMATION OF SOIL In approaching the study of agriculture one finds that the subject naturally arranges itself in a certain order, which can perhaps best be traced by working backwards. Live stock presuppose crops, and these imply considerations of tillage, tending, and harvest- ing. Before, however, a crop is sowed or planted, a farmer has given consideration to seed, manures, and the sequence of crops. ' Then, again, in many cases land cannot be cropped till it has undergone an ameliorative process, such as liming or draining; and finally we get back to the soil itself, with its varied properties and complex origin. Beginning, therefore, with the soil, and working up to the crop, we may first of all look — at what soil is and how it has been formed. 9 10 AGRICULTURE If we go back far enough in the history of the earth we reach a time when there can have been no soil, for the reason that there was not even rock from which to form it. The theory with regard to the evolution of our earth, that finds most acceptance, assumes that at one time it was subjected to so high a temperature that everything of which it is composed was in a state of vapour. In the course of ages, as heat was lost, many sub- stances hitherto held in a state of vapour be- came liquefied, and at this stage we can imagine a globe of essentially the same shape as at present, but in a more or less plastic con- dition, and containing no atmosphere as we understand the term. Gradually, as more heat was lost, the surface of this semi-fluid mass solidified, and, as cooling proceeded further, the superficial crust became thicker. When the temperature fell sufficiently it was possible for some of the water vapour to assume the liquid form, and directly this point was reached the formation of soil became possible. Hitherto the rocks composing the earth were all of the class called igneous, that is to say, they had crystallized out of a molten mass, or were of the ashy character of which lava is a modern representative. But directly water assumed the liquid form it. | THE FORMATION OF SOIL il collected in the hollows to form seas and lakes, or flowed off the surface by whatever channels offered the opportunity of movement. Such flowing water eroded the solid rock, as streams do at the present time, and the particles thus involved in the current were ultimately deposited in lakes and_ seas. _ These deposits in the course of time hardened to form what are called sedimentary rocks, which now constitute a large part of the earth’s crust. But it is well to remember that the inorganic constituents of such rocks have all been derived directly or indirectly from igneous rocks. Sedimentary rocks, formed directly from igneous. rocks, have often in their turn been attacked by running water, and their constituents, re-sorted in the shape of sand, grit, and silt, have been dropped in the estuaries of rivers and streams, again to form sedimentary rocks. _ If we dig into the earth’s surface at any point it is not long till we pass through the superficial soil and reach harder material. The transition from soil to the harder material underneath is generally more or less gradual ; and, having reached the subsoil, we become aware, as we go deeper, that even the subsoil _ is softer above than below, until at a depth of, it may be, a foot or two we reach practically 12 AGRICULTURE -solid rock. From such solid rock, whether it be igneous or sedimentary, the soil that we cultivate in our fields has all been derived, sometimes directly, in other cases through the agency of running water, as in the case of alluvial soils. The sequence of changes from solid rock to cultivated soil can be best studied by inspecting a section that is exposed in the operations of quarrying. Proceeding upwards, we find that immediately over the solid rock there are large masses of stone with but little soil between them. These stones were at one time part of the solid rock, but, by the operations of certain weathering agents, they have become detached from the main body of rock. As we go farther up we find that the stones become scarcer and smaller in size, so that the spaces between the stones are larger and the volume of soil greater. Then, still farther up, the stones are even smaller and fewer, and in the top 8 or 10 inches —which is the material stirred by the plough and other agricultural implements—large stones may be entirely absent or difficult to find. This gradual conversion of solid rock into tillage soil is brought about by the opera- tions of natural forces, few in number and THE FORMATION OF SOIL 13 simple in character. These so-called weather- ing agents may be grouped as follows :— First, variations of temperature—in other words, the lower temperature of winter as compared with summer, and the greater warmth of the day as compared with the night —have had much to do with the breaking up of rocks and the disintegration of stones. This result would not have followed, to any great extent, if rocks and stones were ab- solutely uniform throughout; but this is far from being the case, most stones, and the rocks from which they have been derived, being complex in composition and containing many substances. One of the simpler rocks is granite, the main constituents of which are quartz, felspar, and mica, and these three substances show varying degrees of expansion and contraction under changes of temperature, that is to say, they do not all expand and contract equally. It is evident, therefore, that, even if a rock hold no more than two or three substances, there must be a strong tendency for the constituents to work apart, so that cracks or fine fissures are formed where the different substances come into con- tact. Whenever a rock or stone is no longer solid, but is traversed more or less by a net- work of fissures, even if they are so fine as 14 AGRICULTURE | hardly to be seen, a stage has been reached when the operations of other weathering agents become possible. Hitherto, water, for instance, has been unable to penetrate the mass, and, although it may have been operative on the surface, its power of dis- solving the constituents of the rock or stone has been but limited. But directly water is permitted to gain access to the interior, its power as a weathering agent is greatly in- creased. Water acts in various ways in the formation of soil. In the first place it is an almost universal solvent, so much so that there are few substances that it cannot attack and dissolve to a greater or less extent; and it is evident that if some substance easy of solution is removed from a rock or stone, the rock or stone is honeycombed and weakened in the process, and its power of resistance to other forces is correspondingly diminished. But water also acts chemically upon rocks, converting certain constituents which have no water in their composition into compounds in which water plays an essential part. This change is called by chemists ‘‘ hydration,” and can be illustrated by various familiar examples. One can, for instance, take as an illustration the slaking, or, as a chemist would say, the hydration of lime. Every one THE FORMATION OF SOIL 15 knows that when freshly burned lime is brought into contact with water it absorbs a cer- tain amount, and in the process swells up, and finally crumbles down into a dusty, powdery mass. ‘The water, as such, has disappeared, that is to say, we might add a gallon of water to a heap of burned lime, and although the water was manifestly absorbed by the lime we should be left with lime as dry as the substance with which we started. A small proportion of the water may have escaped into the air in the form of vapour, but most has been taken up by the lime to form a new chemical compound. We start with what is known chemically as oxide of lime, or anhydrous calcium oxide, a substance con-. taining only calcium and oxygen, and we end with a substance which the chemist calls hydrated lime, which is still calcium oxide but now united chemically with a certain amount of water. During this change two things are to be noted, the one, that the lime has undergone considerable increase in volume, and the other, that it has crumbled down in the process. That the slaking of lime is accompanied by increase in volume is evident from various familiar examples. For instance, if we fill a pail with lime shells and pour water upon it, we find that when the lime 16 AGRICULTURE is slaked the pail is no longer able to contain it. Sometimes a farmer has an illustration thrust upon his notice when he purchases lime for agricultural purposes. The railway waggon is filled at the lime-kiln, and is prob- ably dispatched unprotected by a water- proof covering. During the journey, occupy- ing a day or more, heavy rain may fall, and the lime will be more or less slaked, so that when the waggon arrives at its destination it may be found that a considerable amount of lime has been spilt on the journey through swelling up and falling over the side of the waggon. Many other substances besides lime are capable of combining with water in a similar manner, and some of them are present in rocks. One such substance is calcium sulphate, which like lime is capable of chemi- cally combining with water, and in the process is converted into the material called gypsum, undergoing in the change considerable in- crease in volume. Rocks also in many cases contain what are called anhydrous silicates, namely, substances holding silica in com- bination with some other material, but possessing no water. These silicates can, like burned lime, absorb water and increase in volume; and it is evident that if a rock contains any such substance it will be rapidly _ THE FORMATION OF SOIL 17 disintegrated, provided water can gain access to its interior. Such entrance of water is facilitated by the cracks that are formed as a result of the unequal expansion and contraction that is associated with variations of temperature. Water also acts powerfully as a disrupting agent through the agency of frost. A vessel may contain water without injury, but a different result will ensue if the water is subjected to a temperature sufficiently low to convert it into ice. During the. change . the volume of the water is materially in- creased, and so powerful is the pressure thus set up that no ordinary vessel is able to resist it. The result is seen in the bursting of water-pipes, and in similar phenomena. Directly water enters a stone to fill up the interstices, the fate of that stone depends upon the occurrence of frost. So long as the water remains in a liquid form its effect is but slow, but whenever it is converted into ice the parts of the stone are pushed asunder, and when a thaw comes, and the ice is reconverted into water, the hardest stone may crumble down into a shapeless mass. This effect of water is undoubtedly one of the most powerful agencies in the formation of soil. 18 AGRICULTURE In considering the part played by water, mention must also be made of its action as an eroding agent. No one can visit a hilly district where streams are abundant without observing that they flow in well-defined channels, and one may also sometimes find that they have cut a narrow passage in the solid rock. So long as the water is clear, — its power of deepening its passage is but limited; but directly a stream becomes turbid, that is to say, as soon as it carries solid material in suspension, its power of erosion is greatly increased. Streams, which when at summer ‘level are comparatively placid, may, during times of flood, become raging torrents, carrying with them large stones and rock débris. Movement of such bodies over the stream’s bed is accompanied by great erosion, and the particles knocked off the stones themselves, or detached from the rocky bottom, are borne along by the water, to be deposited under quieter conditions, such as prevail in a lake or in the sea, or on the fields (haughs) which the flood may reach. The silt so deposited forms alluvial soil, which in many cases is highly fertile. — Another of the natural agencies at work in disintegrating rocks and stones and pro- ducing soil is oxygen. This gas, which is AN ; THE FORMATION OF SOIL 19 present in the atmosphere to the extent of about twenty-one per cent., has the power of uniting chemically with most substances, the result in many cases being the de- struction of the body thus affected. The destructive action of oxygen is illustrated in the process of ordinary combustion, as, for example, where a heap of thorns is con- sumed by fire But destruction though slower is no less complete where the process is not associated with visible fire. Iron, for instance, when exposed to the atmosphere, ‘ eorrodes and becomes rusty, the conversion of metallic iron into rust being essentially of the same character as the destruction of a heap of brushwood by fire. Whereas iron is a highly resistant body, the rust which oxygen forms is easily crumbled and is markedly non-resistant. Not only may pure substances like iron combine with oxygen and be converted into what chemists call oxides, but certain compounds, e.g. sulphides, may unite with more or less oxygen and be converted into other compounds, as, for instance, sulphates. In stones and rocks there are many substances which can com- bine with oxygen, and the compound so formed is in most cases easily disintegrated, as compared with the original material. If 20 AGRICULTURE one examines a heap of rough land-gathered stones lying by a roadside, one will often find that they are more or less yellow or red on the surface. When they are broken in the process of preparation as road-metal, it is possible to trace a gradual transition from the red, friable surface to a dark, crystalline centre. The dark centre is comparatively unoxidised, whereas the outer layers of the stone have been in contact with the oxygen of the air, which has entered into com- bination with, amongst other things, the iron that is present in the mass. The result of such combination ‘is the formation of rust, or of some other form of iron oxide, whose friability greatly assists the conver- sion of the stone into soil. One of the most powerful weathering agents is carbonic acid gas. This substance acts chiefly through the increased power of solu- tion that it imparts to water. Whereas pure water will dissolve most things, it dissolves them in many cases very slowly, — but when water is charged with carbonic acid gas its power of dissolving all bodies, in- cluding the constituents of rocks, is greatly increased. Compared with oxygen or nitrogen, carbonic acid gas is extremely sol- uble in water, that is to say, a given volume THE FORMATION OF SOIL 21 _ of water can absorb and retain a large pro- portion of this gas. The water in the soil _ obtains its carbonic acid gas in various ways. In the first place, in falling through the air, rain-water dissolves a certain amount of this gas, which it carries in solution to the soil, where it comes into contact with the stones and rocks. In proportion to the amount _of oxygen and nitrogen present in the atmo- sphere, the quantity of carbonic acid gas is very small, but, as the affinity of water for carbonic acid gas is very much greater than for the other constituents of the atmosphere, it follows that the gaseous substances dis- solved from the atmosphere by the falling rain are relatively much richer in carbonic acid gas than the atmosphere from which they have been derived. _ The water in the soil, however, derives the bulk of its carbonic acid gas from the supplies _ which are liberated during the oxidation of _ vegetable matter in the soil. Soil always contains more or less vegetable matter, and in many cases a large amount is present, as, for instance, where soil is rich in humus, derived, it may be, from peat, or from decom- posing turf, or from the residues of previous crops, or from farmyard manure. These organic substances, calculated dry, generally ee AGRICULTURE contain about fifty per cent. of carbon, and in the process of decay this element unites — with oxygen to form carbonic acid gas. The air present in the interstices of the soil, therefore, is specially rich in this gas, and water in the soil has full opportunity of taking up such gas and of thereby adding — to its powers of solution. Other things being equal, there is little doubt that the more carbonic acid gas there is present in the soil the greater is the amount of plant food © available for the use of crops, such liberation | of plant food being effected through the agency of water charged with this gas. Not only are such substances as potash and phosphates dissolved from the stones and rocks, and rendered available for the use of plants, through the agency of carbonic acid, but even when applied as manures these same substances are more effective in the presence of considerable supplies of carbonic acid. An agency that must be mentioned in | connection with the formation of soil is plant roots, which break down stones and rocks in two ways. In the first place they push their way into the cracks and minute fissures of stones and rocks, and, having gained an entrance, they grow, and _ exert Oe Spi THE FORMATION OF SOIL 28 considerable disruptive force. The break- _ ing down of rocks and stones in this way is a _ purely mechanical process. But plant roots also assist in the formation of soil by parting - at their apex with an acid fluid—largely carbonic acid—which attacks stones and rocks, and assists in the solution of their contents. Over large areas in the British Isles the - soil of our fields owes its origin to the action of glaciers, which at one time filled our valleys to the depth of hundreds of feet. With the ‘exception of the higher mountain ranges, the whole of Great Britain and Ireland was heavily glaciated as far south as the Valley of the Thames. By the action of the moving ice the hills were rounded off and planed down, while the valleys were deepened, the whole process being accompanied by severe attrition, the material so rubbed off being deposited in the plains and valleys. If one digs into a field in many parts of the country, especially in the North, one soon comes upon a stratum consisting of larger or smaller stones, often smoothed, and of very diverse character, such as limestone, shale, sandstone, granite, whinstone, and even coal. These stones and boulders, which had, in some cases, been carried by the ice for hundreds 24 AGRICULTURE of miles, are intermixed with finer material, such as clay and grit. When the ice-sheet melted, and this boulder-clay became ex- posed to the weather, its upper layers under- went the weathering changes that have just been described, the result being the soil that we till on many of our fields, which rests on a subsoil of glacial material in much the same condition as the glaciers left it thousands of years ago. CHAPTER Ii THE PROPERTIES OF SOIL Havine briefly considered the formation of soil, we may now conveniently turn to certain physical and chemical properties that it pos- sesses, which are of much importance in their bearings on the nutrition of plants and the cultivation of farm crops. One property that soil has is simply the power possessed by the particles of sticking together, or, as it is called, the property of cohesion. At one end of the scale we have dry sand, which is practically destitute of cohesiveness; while the other extreme is occupied by plastic clay, which exhibits so arr al pe eae Renee THE PROPERTIES OF SOIL 25 much cohesiveness that it can be moulded into any shape that we may desire. As so often happens, the best conditions, from the agricultural point of view, are not to be met with at either extreme, in fact a soil with little or no cohesiveness is almost _as profitless a subject as one of the con- ‘sistency of Gault Clay. When a soil possess- ing. too little cohesiveness is taken in hand for purposes of cultivation, the first step taken by the farmer or gardener is to introduce something into the: soil that will give it “body,” and assist in keeping the particles together. Sandy soil can be improved by the addition of clay, and at one time the operation of “claying’’ land, in other words the ad- - mixture of fifty loads or more per acre of clay with the surface soil, was not an uncommon ameliorative process. But such an operation involved more outlay for labour than is justifiable under present conditions, so that, except under very exceptional circumstances, one does not now find that sandy soil is being treated in this way. But what farmers and _ gardeners are thoroughly alive to, is the necessity of taking steps to increase the percentage of humus, that is to say, decom- posing vegetable material, as represented by farmyard manure, decomposing turf, leaf 26 © AGRICULTURE mould, green manure, and the like. Such material, by binding together the particles of sand, does much to diminish the excessively non-cohesive condition of sandy soil. In the case of strong clay, which is too cohesive, much may be done to produce a more crumbly consistency by early ploughing, and the exposure of the rough furrow to the action of winter frost and ‘spring sun. Even the most plastic clay crumbles down in the course of the winter; and in spring, if the con- ditions are sufficiently dry, it may be almost mealy in character. The alternations of tem- perature during winter and spring, the dis- ‘integrating action of frost, the corroding effects of the oxygen and carbonic acid of » the atmosphere, and other natural agents, have been at work, mellowing the soil, and producing what every farmer likes to find in abundance in spring, a good tilth. But this desirable condition of the soil can be very easily destroyed by injudicious treatment, and every experienced farmer and gardener knows that the most beautifully tilthy soil may be converted into a plastic, sticky mass, too cohesive when wet and too hard when dry, if strong land is worked when out of condition. It is in spring that one must be most careful, at a time, namely, when the THE PROPERTIES OF SOIL 27 chances of a spell of corrective frost are past ; mistakes in autumn are of less account, and the less so the more severe the winter that follows. In the case of clay, as in the ease of sand, the addition of humus does much to improve its character in the way of eohesiveness; for whereas this substance “Increases the cohesiveness of sand it has the opposite effect on clay, making it more easily broken down and brought into a desirable mechanical condition. Then, again, not only must the particles of soil possess the property, within limits, ‘of sticking together, but they must also have the power of retaining water. Soil may be ‘practically sterile either because it contains too little water or because it contains too much, the proper. degree of moisture as a rule being reached when the soil feels damp to the hand. It is on the water that is held between the soil particles that plants feed, and through which agency they derive all the “mineral material which is vital to their existence. In the case of sand, the capacity of the soil to retain water is increased by the addition of humus, whose power of absorbing water is much greater than that of sand itself. Clay also is improved by the addition of humus, which, to some extent, loosens the parent, 28 AGRICULTURE soil and facilitates the entrance of air. Its presence, also, tends to diminish the resistance offered by the soil to the extension of the root range of plants, and to the upward growth of young seedlings. Intimately associated with the capacity to retain water is the power that soil, in ~ common with many substances, has to raise — water from deeper layers, and to attract it horizontally from one point to another. Did | the soil not possess the power of bringing water _ from the subsoil to the region where plants dispose their roots, our farm and garden crops would seldom be able to survive an ordinary summer. Experiments have shown — that many crops in the course of a growing season part with much more water to the air than directly reaches the land during that period in the form of rain, and it is only by tapping underground supplies through the agency of capillarity, that crops are able to grow during weeks and even months of © persistent drought. The power possessed by soil of raising water against the force of — gravity can be illustrated by taking a lump of ' dry clay and dipping the lower part into a bowl of water, when it will be seen that a certain amount of the water instantly rises into _ the clay, which, if held long enough in contact — THE PROPERTIES OF SOIL 29 with the water, will be found to become entirely saturated. In respect of this property soils vary greatly. Some can raise water rapidly but not to a great height, others will _ raise water slowly but, given time, the water _ will reach a much higher level than in the other case. It has been found that the property largely depends upon the fineness of the particles of soil, or, in other words, on the size of the interstices between the particles. Nowadays it is usual to speak of the property, by the exercise of which water rises in the soil, as “surface attraction,”’ ‘each particle of soil covering itself with a thin film of water, which diffuses from particle to particle until the whole mass is equally moist. Coarse sand, for instance, does not raise water so effectively as sand with finer grains; clay, with its fine particles, _Yaises water rather slowly but to a com- paratively great height. Humus facilitates the rising of water and, therefore, improves the conditions of sand. Of all the soils with which a farmer has usually to do, fairly pure _ sands are most likely to suffer from the effects of drought in a season when rain is deficient. Much, however, can be done to improve matters by increasing the supply of humus, | so that a sand, comparatively barren in its 30 AGRICULTURE — natural condition, may become most useful for cultural purposes if steps are taken to increase the stock of decomposing vegetable matter in it. | | As the outcome of experience, methods of cultivation have been adopted whereby this property of soil is utilized to the fullest extent. When seed is deposited in a field or garden, and is covered with an inch, more or less, of soil, it is desirable that it shall without loss of time be sufficiently supplied with water, so that no delay shall occur in germination. By rolling land after the seed is sowed, or by compressing a seed-bed with the back of a spade, the cultivator brings ‘the particles of soil on and near the surface of the ground — closer together, and thus, by diminishing the interstices in the soil, increases the property of capillarity. As a result, water rises from the subsoil right up to the surface of the ground, and in its passage comes into contact with the seed, which by absorbing moisture undergoes the changes which collectively result in what is called germina- tion. It is true that by inducing the water to mount to the surface of the ground a certain proportion escapes into the air and is lost to the crop, but such loss is inseparable from the advantages that are gained in pro- THE PROPERTIES OF SOIL 31 viding the seed with the water that it re- quires. When the seed has germinated, and has pushed its roots some inches into the soil, the necessity no longer exists of in- ducing water to rise to the point in the soil where the seeds had been placed, and it now becomes more desirable to conserve water in the subsoil than to encourage it to rise to the surface. The plant by means of its roots can now draw water from comparatively deep layers, and what farmers and gardeners generally do at this stage is to hand-hoe or . horse-hoe the surface of the ground, whereby the interstices in the soil are increased in size. In this way the power of capillarity is diminished, and water is prevented from rising to the surface and escaping into the air. A loose covering of well-disintegrated soil is called a soil-mulch, and ‘such a covering will prevent the upward escape of water in much the same way that a mulch of rough manure laid upon, for instance, a rose-bed, will conserve water for the use of plants growing there. _ The utilization and conservation of rain- water and melted snow, through the agency of cultural methods, has received much attention during the past few years in most _ of the drier regions of the world. In certain 32 AGRICULTURE areas of Canada and the United States, for instance, the annual rainfall does not exceed 10 inches, a quantity quite insufficient to meet the requirements of such a crop as wheat. In these districts it is now a common practice to crop the land only once in two years, the intervening year being utilized for the purpose of collecting and storing water in the soil for the use of the crop during the succeeding year. During the year of bare fallow the field is frequently stirred to the depth of 8 or 4 inches by the cultivator and harrows, and may once or twice be shallow ploughed, the result being that the loose, dusty condition of the surface soil prevents water rising to the surface, and escaping . into the air.. The rains and snows of one > year are thus added to the atmospheric pre- cipitations of the next, and by this means crops can be grown in alternate years under conditions that would otherwise prevent their being grown at all. In the drier parts of Britain much of the attention of the cultivator should be given to the conservation of soil moisture. Not only should ground not yet under a crop be lightly cultivated in spring, but during summer also, when a crop is being grown, attention should be given to careful inter- : eee ‘ S74; va rye THE PROPERTIES OF SOIL 33 cultivation—assuming the crop is drilled— so that as little water as possible shall be allowed to escape into the air, except through the leaves, and such water, of course, has done all the work of which it is capable. If, on the other hand, the soil is allowed to become encrusted, water rising from the sub- soil by capillarity has no difficulty in reaching the surface and is uselessly evaporated into the air. It may be that such loss of water is increased by the growth of weeds, which not only rob a crop of its food, but also . deprive it of a certain proportion of the water which is vital to its existence. The importance of water-conservation has been more recognized of late years by farmers, but in this respect gardeners certainly led the way. Most gardeners know that the require- ments of plants for moisture are almost as well met by the use of the hoe as by the use of the watering-can, in fact in some cases it may be said that the hoe supplies water more satisfactorily than the watering-can, because whereas water falling from a can consolidates the surface, water rising from below produces no such undesirable results. We are apt to associate surface attraction or capillarity with the vertical movement of water, but the same force is equally operative B in a horizontal direction, should the soil at any point become drier than adjacent soil on the same level. When, for instance, a plant is feeding, that is to say, when it is taking in mineral food dissolved in water, its root hairs are draining the soil of moisture in their immediate neighbourhood, Had the soil no power to bring fresh supplies of water into contact with the root hairs, the latter must cease to feed directly they have abstracted. the moisture from the soil in their immediate vicinity. But no sooner is the moisture withdrawn from such soil than equilibrium is upset, and from all directions— from below, from. the side, from. above—the small mass of soil, which has been drained in the way indicated, has the power of attracting water, so that there is a constant movement of moisture towards the tips of the roots, namely, the parts of the plant where water is most required, This water carries with it the potash, phosphates, nitrates, and other plant food required by the crop, and although the solution is a very weak one the aggregate amount of mineral matter and nitrates that passes into an average crop in a growing season may amount to several hundred pounds per acre, It_is this food that nourishes the cells of the THE PROPERTIES OF SOIL 85 plant, and thus helps those of the leaves in their characteristic work of decomposing the carbonic acid gas of the air, which enters into the leaf, chiefly through the minute apertures (stomaia) so abundant on the sur- face of leaves, and also, though to a less extent, on young shoots. It is from the carbonic acid gas of the air that plants get: their carbon, a substance that constitutes about one-half of the dry matter of a crop, all of which has been abstracted from the atmosphere with which the leaves and stems are bathed. The mineral matter may not exceed five per cent. of the dry weight of a crop, and yet it is just as essential to growth as the carbon which is so much more abundant. Mineral matter is all absorbed from solutions in the soil, not enter- ing through any definite apertures in the roots or root hairs, but passing through the bounding membrane of the root hairs, which themselves are lateral outgrowths of epidermal cells. There would be no move- ment of water and plant food from the soil into the roots were it not for the fact that the solu- tions (cell sap) in the root hairs and epi- dermal cells—for some plants have no root hairs—are stronger than the solutions in the soil. But, given these conditions—namely, B2 e6 “°° AGRICULTURE a comparatively strong solution of sugars, etc., in the epidermal cells and root hairs, and a very weak solution of mineral matter in the adjacent soil—the water carrying the mineral food has the power of passing through the membrane and so of getting inside the plant. Having gained an entrance it moves upwards, owing to the fact that water is constantly being expired from the upper part of the plant; and in some way, not yet altogether satisfactorily explained, ~ the water, with what is dissolved in it, moves upwards to replace that which is with- drawn. During the growing season, there is a constantly ascending stream which has its origin in the soil and its destination in the atmosphere. The mineral matter present in this ascending stream is not expired into the air, but is retained by the plant and utilized for its vital requirements. Experi-. ments have shown that for every pound of dry material—mineral and organic—stored up in the plant some hundreds of pounds of water have passed through the plant tissues. The passage of water through a mem- brane, and its diffusion throughout a solu- tion inside, can be demonstrated in various ways.} If, for instance, we take a hollow glass cylinder, 6 inches or so in length, and THE PROPERTIES OF SOIL 87 open at both ends, and place a piece of bladder across one end, subsequently filling it with a strong solution of sugar, and then close*the other end with a similar membrane, we shall find that if the cylinder be placed in a basin of water the membranes will be pushed outwards owing to internal pressure set up in consequence of the movement of water into the cylinder. Or, conversely, we may have the solution of sugar in the basin, and water in the eylinder, when the membrane will be pushed inwards owing to water having passed the membrane and intermixed with the sugary solution in the basin. Cells which are subjected to in- ternal pressure, and whose membrane is stretched, are said to be “turgid ’?; whereas cells with no internal pressure are said to be in a condition of: plasmolysis. The growing shoot of a herbaceous plant, for instance, has its cells in the turgid condition and, consequently, stands erect; but if such a shoot be severed from the plant it speedily becomes limp and droops, because when water can no longer move up the stem to maintain internal pressure in the cells the latter rapidly pass into the condition of plasmolysis. While the requirements of plants as regards water are, to the greatest extent, met by 38 AGRICULTURE the supplies provided directly or indirectly by rain or melted snow, it may be mentioned that soil, in common with many other sub- - Stanees, has the power of condensing a certain amount of water from the vapour naturally present in the atmosphere, and such water is not without influence in the soul. This property of soil may be demon- strated by thoroughly drying a small quantity in an oven and then leaving it exposed in a room. If the weight of the soil be accurately determined immediately after drying, and again after exposing to the air for two or three hours, it will be found that the soil has undergone considerable increase in weight, and it is not difficult to prove that this increase is due to the condensation of moisture from the atmosphere. Certain of the con- stituents of soil, notably humus, have this power to a greater extent than others; while some artificial manures, e.g. kainit and nitrate of lime, act in a similar manner, and to an even greater extent; but it is doubtful whether artificial fertilizers are ever applied in such quantity as to have any appreciable influ- ence upon the total water contents of the soil. The soil has not only interesting and use- ful relationships with water, but certain of its properties as regards heat are also of — THE PROPERTIES OF SOIL 39 vital importance to the life of plants, and to the profitable cultivation of crops. If certain definite weights of such substances as iron, copper, and lead, are exposed to the same amount of heat for definite periods it will be found that the temperature of these bodies varies. considerably, showing either that they have taken up varying quantities of heat or that for the same amount of heat their temperature has responded in varying degree. The property of a body to absorb heat is known as its capacity for heat, the standard of measurement being the capacity for heat, or the Specific Heat, of water. Specific heat may be defined as the quantity of heat which a definite weight of a sub- stanee requires in order that its temperature may rise through one degree of temperature, that of water being taken as unity, The im- portant constituents of the soil show marked variations as regards their capacity for heat, and, according to the proportion in which the constituents are present, soils may be warm or cold. Of all the constituents of. soil, water is the one which requires most heat in order that its temperature may rise through a definite number of degrees ; that is to say, it stands at the top of the list as regards specific heat. The specific heat of water 40 AGRICULTURE being represented by 1,—that is to say, being taken as unity,—that of the other constituents of the soil will be represented by a fraction of 1. Thus the specific heat of humus is about 0°5, the specific heat of carbonate of lime and clay about 0°25, while the specific heat of sand is no more than 0°2. This means that, whereas 1 lb. of water would rise in temperature 1° when exposed to a certain amount of heat, 2 lb. of humus, 4 lb. of clay or carbonate of lime, and 5 lb. of sand would rise to the same temperature when exposed to the same amount of heat. In other words, substances of low specific heat, like sand, are readily warmed when exposed to the rays of the sun, whereas a soil containing much humus is not so easily heated, and a soil that holds a large quantity of water remains coolest of all. Wet soils, therefore, are cold. soils, while sandy soils are warm, so that it is evident that the specific heat of soil must have a marked influence on the rapidity of germination of seed, as well as on the growth of plants, and the time of harvest. Within limits it is an advantage that a soil should be warm, but in the case of such a soil as sand the tempera- ture may rise to too high a point, with the result that crops may ripen prematurely, and THE PROPERTIES OF SOIL 41 the yield may be deficient. It is, therefore, desirable to take steps to raise the specific heat of such a substance as sand, and this can be done by adding to the stock of humus that it contains; for not only does humus in itself keep sand cool, but, being a powerful absorbent of water, it enables the soil to hold more water, and nothing depresses the temperature so much as this substance. The temperature of a soil depends not only on its specific heat, but also upon its power to absorb or reflect heat, and this property is influenced to a considerable extent by its colour. Other things being equal, a white or light-coloured soil is a cool soil, because the sun’s rays are not so readily absorbed by a white surface as by a dark. If, for instance, two vessels are filled with soil, the surface of which, in the one case, is whitened by a _ dusting of lime, while, in the other, it is blackened with a sprinkling of soot, it will be found, after exposure to sunlight, that the temperature of the soil with the dark surface is higher than the temperature of the same soil which has been sprinkled with lime. This property of soil and other bodies, whereby their temperature is in- fluenced by their colour, is illustrated in _ practical life by the fact that human beings 42 AGRICULTURE wear lighter-coloured garments in summer than in winter, the intention being to reflect the sun’s rays in summer and to absorb them in winter. It may often be noticed, also, that in warm districts the roofs of houses aré painted white in summer, the white colour throwing back or reflecting the sun’s rays, many of which would be absorbed if the roof were black or any other colour but white. The great and immediate source of heat, so far as soil is concerned, is the sun; but the temperature of soil is, to some extent, influenced by heat directly: received from other sources, such as decomposing vegetable matter. Every one is familiar with the fact that a mass of farmyard manure—especially easily-fermentable material like horse manure —has a comparatively high temperature, and this source of heat is utilized in gardening practice in the propagation of plants in frames. If the same amount of manure were spread over a considerable area of ground, one might be disposed to think that it was providing no heat; but, in point of fact, the amount of heat given out during its decomposition by, say, 10 tons of farm- yard manure is precisely the same, no matter whether it is concentrated below a garden THE PROPERTIES OF SOIL 43 frame or is spread over an acre of land. Probably the heat liberated in the soil by the decomposition of such a moderate dressing of manure as 10 tons per acre would be difficult to detect by means of an ordinary thermometer, but if the dressing of manure were 50 tons or more per acre—as is not uncommon in intensive horticultural and agricultural practice—the influence on the temperature of the soil would be quite appreciable. The decomposing remains of a former crop, as represented by plant roots, stubble, etc., also give out heat, although not so rapidly as more easily decomposable farmyard manure; but still, as a source of heat, they have to be taken into account in considering the various factors affecting temperature. The production of heat in this way is a consequence of oxidation, that is to say, it is due to the union of the oxygen of the air with some substance which either - contains no oxygen, or contains less oxygen than it is capable of combining with. Although vegetable matter oxidizes more rapidly than other substances in the soil, it may be mentioned that low oxides of iron and other elements can take up more oxygen, and, in the process of combining, heat is liberated to affect bodies in its neighbourhood. 44 -_ AGRICULTURE i Then, again, it must not be forgotten that there is an enormous amount of heat in the centre of the earth, proof of which is furnished by hot springs, and active voleanoes, and also by the fact that as one goes down the _ shaft of a mine the temperature rises steadily and fairly rapidly. On account of the earth’s crust being a very bad conductor, the heat present in the centre of the earth is conducted outwards very slowly, but that the internal supply of heat in the earth has to be reckoned with cannot be doubted. | One of the most important properties of soil is concerned with its power of retaining, absorbing, or fixing plant food from solutions. This property is something entirely different from the power which soil, in common with many other substances, possesses of mechanically filtering out materials held in suspension in water. When a substance is in solution it is quite inseparable by mechani- cal processes of filtration, but it is known that soil possesses the power of removing certain of these substances and of retaining them in its mass. If, for instance, one were to fill with soil a series of glass tubes open at each end, having previously closed one end with wire gauze or muslin, and if certain THE PROPERTIES OF SOIL 45 solutions of chemical substances that serve as plant food were subsequently poured on the top of the soil in these tubes, it would be found that in some cases the solutions that drained away from the bottom of the cylinders were weaker than the solutions that had been poured in on the top. Clearly, therefore, the soil had, in some way or other, abstracted material from the solutions. In other cases it would be found that the solutions draining away from the foot of the tubes were of as great strength as those which were poured in above. It is evident that substances which are absorbed by the soil are in least danger of being lost in drainage waters, while those that are not so absorbed have more chance of escaping, and of being lost so far as crops are concerned. The three most important elements of plant food that are supplied in artificial manures behave somewhat differently as regards this property of soil. Potash and phosphoric acid, even in a soluble form, when applied in moderate quantities, are not in danger of being lost to any appreciable extent. The danger, there- fore, of loss through heavy rainfall is not great in the case of these substances. As regards nitrogen, it is found that when this is applied in the form of ammonia, e.g. sulphate 46 | AGRICULTURE = of ammonia, it is fairly well fixed by the soil, whereas when the nitrogen is in the form of nitrie acid, e.g. nitrate of soda, the soil has practically no power to remove it from solutions, Lime, magnesia, and soda are also but little removed from solutions, and therefore these substances, in common with nitrates, bulk comparatively largely in the drainage water of our fields. In connection with this subject it may be mentioned that the soil absorbs relatively most from weak solutions, while its power of absorption is reduced almost in proportion to the strength of the solution. If, for instance, a solution containing one-twentieth per cent. of sulphate of potash is poured through soil, about one-half may be removed ; but if the solution is twenty times as strong, that is to say, if the solution is of the strength of one per cent., the percentage of potash absorbed will only be about one-third of the relative quantity removed in the other case. There is therefore greater danger of loss by drainage where one applies a very heavy manurial dressing than where one is giving only moderate doses. The causes of such removal of substances from solution are rather various, but in the case of mineral substances the agents that THE MAIN TYPES OF SOIL 47 affect the fixation are the lime, iron, and similar bases that are naturally present in abundance in all soils. In the case of ammonia it is probable that the most im-. portant fixing agent is humus, which, as is well known, has great power of mechanically storing up ammonia in its tissues. We have a good example of the affinity of humus for ammonia in the fact that where moss litter— which is a form of humus—is used in stables the atmosphere is much less redolent of ammonia than where the litter is straw. As regards soils, it is found that the least power of absorption is possessed by sand, while the property is most conspicuous in strong loams, clay, and soils that contain much decomposing vegetable matter. CHAPTER III THE MAIN TYPES OF SOIL WHILE soil is in many respects a very complex substance it can, from the agri- cultural point of view, be regarded as com- posed mainly of four substances, that is to say, in all soils one or other of these four 48 AGRICULTURE materials constitutes the bulk of the mass. In some soils the main ingredient is sand or quartz, in others it is clay, in some it is carbonate of lime, while in soils of the fourth class the predominating material is humus. Soils whose main constituent is sand or quartz grains has definite and easily recog- nizable properties. In the first place it undergoes little if any further change under the processes of weather, for the reason that the siliceous material which forms the bulk of its mass is not decomposable by the action of natural agents. It is said to be light, in the sense that the labour of working it is easy. It is generally dry, because its mechan- ical condition permits of the easy drainage of water. It is warm, partly because it has a low specific heat, and its temperature therefore rises quickly under the influence of sun or warm air, and partly because it. holds little water, and therefore this substance of high specific heat is not present to keep it cool. Not only does water, in conse- quence of its high specific heat, prevent the temperature of soil from rising, but it also tends to make soil cool, owing to the fact that where one has water one has always more or less evaporation, and the conversion of water from the liquid into the gaseous diptet THE MAIN TYPES OF SOIL 49 condition is always accompanied by the disappearance, in an easily perceptible form, of heat, This result can be readily illustrated _ in a variety of ways. If, for instance, we moisten the back of the hand and then blow upon the moistened surface, so as to cause rapid evaporation, we notice that the skin is manifestly cooled to a greater extent than would be the case were the moisture allowed to evaporate more slowly. A flask containing liquid can be kept cool in hot weather by surrounding it with some absorptive material . like flannel, and if this be saturated with water, the latter will evaporate when freely exposed to the air, and the withdrawal of heat from the liquid in the flask will be indicated by a fall in temperature. During dry weather, when water is removed from sand by evaporation or otherwise, the soil does not shrink to any great extent, and, consequently, sandy soils never show cracks ‘ during periods of drought. Owing to the comparatively small amount of water that sand can take up and retain, and also because of the ease with which it parts with moisture, crops are apt to ripen prematurely on such soil and are always deficient in yield during seasons of low rainfall. Other things being equal, therefore, sandy soils give their best 6 % 83=—S——~ a ¥ i ae = ifs x a ct Be ee (ax ! - ¥ AMELIORATION OF LAND 95 _ be assumed, satisfactory results, but at _ present it is on the whole rather rare to _ find land being thus treated. The quantity - used was often as much as 20 or 80 tons per acre, and the labour of digging, carting, and spreading this amount involved a high outlay that few farmers would now care to face. The effects of applying lime in any form a may thus be shortly summarized. It attacks the humus with the ultimate formation of nitrates, and where land is rich im organic matter this is probably its main effect. It also reacts upon the natural silicates in the soil and liberates a certain amount of potash, which then becomes available as plant food. Lime also tends to sweeten soils, that is to say, it neutralizes organie acids and induces an alkaline reaction, a condition of things which is inseparable from high fertility. By | neutralizing acids, lime also makes soil unsuitable for the life of the organism that F causes finger-and-toe in turnips and other | cruciferous plants. Lime has also useful physical effects on soil, making clay more _ friable and therefore more easily worked, and raising the absorptive power of lighter soils, but it is doubtful whether these results alone will often justify the heavy expenditure necessary to secure them. 96 AGRICULTURE An ameliorative process that is still largely practised on the heavy lands of England, especially in our drier districts, is Bare Fallowing, that is, the leaving of a field without a crop during a whole season. It is a process that is not now so common as formerly, though, in 1910, in Bedfordshire 1 acre in 11 of the tillage area, in Huntingdon 1 acre in 12, and in Essex 1 acre in 13, was under bare fallow; which contrasts with 1 acre in 876 in Cumberland, and 1 acre in 1516 in Haddington. The average for the whole of England in 1910 was 1 acre under bare fallow for 31 acres of tillage, or fully three per cent.; while for Scotland the corresponding figures are 1 to 546, or less . than one-fifth per cent. It is extremely doubtful whether so high a percentage of bare fallow as prevails in certain districts of England is justified, for if land cannot be kept under cultivation except by periodically missing a crop, it is probable that, on the whole, it would pay better to lay the land away to permanent grass. Then, again, it *, < e wk Se La > ~ es > * = - rene PRINCIPLES OF MANURING = 105 which it dissolves from the soil in a definite time, and under definite conditions, being taken as an indication of the percentage of these substances that is immediately available as the food of crops. It cannot be denied that the results thus obtained are of con- siderable value as a guide to manuring, ' especially under extreme conditions; that is to say, such a method of analysis enables one to conclude with considerable confidence whether a soil undoubtedly requires or does not require the addition, let us say, of phosphoric acid or potash. But in the case of a soil which is neither very rich nor very poor in these substances, it is doubtful whether such determination of *‘ availability ” is of much value as a guide in the practice of manuring. While it cannot be said that we apply manure to land in order to grow a crop, or to furnish something previously non-existent, it can with confidence be said that manuring is undertaken in order to obtain a full crop, in other words, a crop that is economically profitable. It has always to be remembered that a large part of the yield of any crop goes to meet the standing expenses of the farm; and if the yield is only sufficient to meet such expenses it is evident that 106 AGRICULTURE no profit will remain to the cultivator. But if the yield can be considerably increased at a reasonable expenditure on manure, it will be found that the net profits of the farm are rapidly improved, because the standing expenses of growing large crops are pro- portionately less than those of producing small ones. ? In considering the principles of manuring, one must give particular attention to the Law of Minimum, which may be stated thus: That the yield of a crop depends upon the available supply of that essential element of plant food that is’ present in least amount. Put into other words, the law im- plies that no superabundance of plant food generally can compensate for deficiency in an essential element. In popular language, the law may be illustrated by a chain, whose strength is necessarily determined by the weakest link. All the higher plants, and therefore all farm crops, require to have access to ten elements of food, that is to say, no plant can grow unless every one of these ten elements is present, and no crop can give a full yield unless they are all present up to the requirements of the crop. These elements are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, . ie PRINCIPLES OF MANURING 107 magnesium, iron, and calcium. But although every one of these ten elements is necessary for the growth of plants, we do not require to supply them all in manure, because, in the atmosphere or in the soil, several are naturally present in abundance. Except under unusual circumstances, the only three substances that the farmer requires to con- sider, from the point of view of manuring, are nitrogen, phosphorus, and potassium, the two latter being usually designated under the name of their oxides, and called, re- spectively, phosphoric acid and potash. No doubt there are exceptional cases where lime (calcium) is so deficient in the soil that crops cannot obtain all their requirements; but, as a rule, lime is employed rather as an ameliorative than as a directly nutritive substance. Again, magnesia (magnesium) may occasionally fall below the necessary quantity, but it is rare that actual experi- ment has proved this to be the case. Confining our attention, therefore, to the three elements that are of most importance in manuring, we find numerous illustrations of the working of the Law of Minimum in the published results of the station at Rothamsted. Thus, the average yield of hay for upwards of forty years was 23°2 cwts. per acre without 108 AGRICULTURE manure, 26°1 cwts. where about 34 cwts. of ammonium salts were annually employed, and 23°3 cwts. where about the same quantity of superphosphate was used; whereas from the plot receiving both ammonia and super- phosphate an average yield of 35°5 ewts. of hay was annually obtained. These figures show that phosphoric acid used alone in the form of superphosphate has produced the quite insignificant increase of one-tenth cwt. of hay, and although nitrogen, in the form of am- monium salts, similarly employed, has done a little better, the increase over the un- manured land is only 2°9 cwts. of hay per acre. Qn the other hand, when super- phosphate was added to ammonium salts it was accountable for 9°4 cwts. of hay, and when ammonium salts were added to super- phosphate the yield of hay was increased by 12°2 cwts. The aggregate increase, in fact, of these two substances used on separate areas was only 3 cwts. of hay, but when applied together to the same land they pro- duced an increase of hay amounting to 12°83 ewts. These figures show that this land at Rothamsted is deficient in both phosphoric acid and nitrogen, so that when only one of these substances is employed the increase is quite insignificant, for the reason that it is vance + PRINCIPLES OF MANURING 109 the necessary element present in least amount (in this case nitrogen and phosphoric acid respectively) that determines the yield. Similar results appear from the barley experiments, which have been continued since 1852. Whereas 34 cwts. of super- phosphate added only 4°8 bushels to the crop ~ when used alone, it was responsible for an increase of 13°4 bushels when used as an addition to ammoniacal manure. Similarly with regard to 200 lb. per acre of ammonium salts, which, when used alone, increased the crop by 11°2 bushels, whereas when added. to superphosphate they were accountable for 19°8 bushels. Not only does the Law of Minimum in- dicate that an intelligent farmer should take steps to discover which is the weakest link in the chain of nutritive substances in his land, but it also shows that weakness in any one link cannot be compensated for by strengthening other links. If, for example, the natural supplies of nitrogen in the land are deficient, no improvement in the crop ean take place by the use of additional supplies of phosphoric acid or potash. The Law of Minimum is usually considered in relation to manures, but it is equally applicable to any other essential condition 110 AGRICULTURE of growth. Not only do plants require to be fed with suitable substances, but their growth is also determined by other necessary conditions, as, for example, a plentiful supply of oxygen, a suitable temperature, and the requisite degree of moisture. If, for instance, oxygen is deficient in the soil, no conditions of temperature, however favourable, will compensate for insufficient aeration. Or everything may be satisfactory save tempera- ture, and, again, growth will be unsatisfactory or non-existent until this limited factor is put right. According to the manurial element that they contain, artificial fertilizers are classified as nitrogenous, phosphatic, or potassic, or a combination of these terms. The two most important manures that furnish nitrogen alone to plants are Nitrate of Soda and Sulphate of Ammonia; but to these there have recently been added two others, nitrate of lime and calcium cyanamide, which are prepared by inducing the free nitrogen of the atmosphere to enter into chemical combination under the stimulus of electric discharges. In addition to the four purely nitrogenous manures just mentioned, there are such subordinate sub- stances as Rape Meal, Blood Meal, etc., but these are of comparatively little importance. PRINCIPLES OF MANURING 111 With a possible choice of at least four nitrogenous manures, varying somewhat in composition and in price, it becomes of importance that farmers should be able intelligently to select the particular sub- stance best adapted for their special require- ments. Up to the present the choice has lain almost exclusively between nitrate of soda and sulphate of ammonia, and on the basis of equal quantities of nitrogen there are special circumstances that point to the one rather than the other as being best suited for any particular case. Something depends upon the crop to which the manure is to be applied. Speaking generally, nitrate of soda acts better than sulphate of ammonia as a top-dressing, partly because when one top-dresses a crop one desires immediate action, and this is got from nitrate of soda, and partly because it sinks more quickly and more deeply into the ground and so comes more © effectively within the range of the roots of the plants. Moreover, when a crop already occupies ground to which manure is applied, chances of waste are reduced to a minimum, and this is a consideration of greater importance in regard to nitrate of soda than to any other manure - except nitrate of lime. Sulphate of ammonia, on the other hand, is “ fixed ” or “ absorbed ”” 112 AGRICULTURE to a great extent by the superficial layers of the soil, and therefore does not reach the roots of a top-dressed crop with sufficient rapidity. Of these two manures nitrate of soda is the better for application to the hay crop, and this chiefly because we have hereto dowith a crop that can only be manured by top-dressing, so that the added plant food amust find its way down through a greater or dess depth of soil before reaching the roots. The superior merits of nitrate of soda, as contrasted with sulphate of ammonia, as a top-dressing for hay, are well illustrated in the long series of experiments conducted on the permanent meadow at Rothamsted. Without exception, nitrate of soda has pro- duced a much heavier crop of hay than ammonium salts, and botanical analysis has shown that the hay is also of superior quality. Nitrogen in the form of ammonia is largely retained in the surface soil, and it has there- fore the effect of encouraging the development of shallow-rooted plants, such as Sheep’s Fescue, Agrostis, Yorkshire Fog, Sweet- scented Vernal, and Smooth-stalked Meadow Grass; whereas nitrate-nitrogen, by sinking deep into the soil, encourages the growth of plants whose roots are similarly disposed, notably Meadow Foxtail, Tall Oat Grass, PRINCIPLES OF MANURING 118. _ Rough-stalked Meadow Grass, and Perennial _ Ryegrass. The herbage, therefore, of the nitrate plots, being deeper rooted, is better _ able to withstand drought; and this charac- _ teristic, combined with the more extensive _ feeding range of the deep roots, has reacted beneficially on the yield. It may be added, b also, that an acid condition of the soil, in- duced by the long-continued use of ammonium salts, has encouraged the increase of Sorrel, and the same cause has markedly repressed the growth of the Leguminose. Other things being equal, sulphate of ammonia is relatively more suitable for application to turnips and potatoes, because in the case of these crops the manure can be thoroughly incorporated with the soil, and, moreover, growth taking place at a time of year when the micro-organisms of the soil are specially active, ammonia is quickly brought into a condition in which the plants can utilize its nitrogen. But although sul- phate of ammonia appears to be relatively well adapted for use on root crops generally, notable exception is furnished by the man- gold crop, which at Rothamsted has re- sponded in a very marked manner to the use of nitrate of soda as contrasted with sulphate of ammonia. The causes of the 114 AGRICULTURE [ superior effect of the former manure are probably rather complex. Nitrate of soda sinks more easily and to a greater distance into the soil, and the roots of the mangold crop, following the nitrate, occupy a much more extended range of feeding ground, and so are brought into contact with supplies of potash naturally present in the soil which they can utilize. While it cannot be maintained that soda can replace potash in the economy of the plant, it is possible that certain physio- logical processes may take place by the aid of soda where potash is not available, and thus the soda of the nitrate. of soda confers a benefit upon the crop which is excluded in the case of the sulphate of ammonia. That there are good grounds for this suggestion appears to be proved by the fact that where- as the mangold crop at Rothamsted responds in a very striking manner to the use of potash in the presence of ammoniacal dress- ings, there is no such marked response where potash is employed in the presence of dress- ings of nitrate of soda. The conclusion would therefore appear to be justified, that in the latter case potash is not so much required, because, as has been indicated, the soda has to a certain extent acted as a substitute. PRINCIPLES OF MANURING 115 __ _ The cause of the superior action of the nitrate of soda may also depend in part on _ the fact that, by encouraging deeper ex- ' tension of the roots, the crop is placed in a _ better position to withstand the effects of _ drought. This cause, however, would operate in the case of all crops, although it may be ' more emphasized with the mangold crop. It may also be mentioned that when nitrate of soda is applied to land, the soda E may displace a certain amount of potash from natural combinations in the soil, and ‘ the potash so liberated will become avail- able for the use of plants. The action of these two manures depends also to some extent upon the character of the soil to which they are applied. There is much greater danger of nitrate of soda being - washed out of the land than is the case with sulphate of ammonia, and therefore, other things being equal, one would be disposed to favour the use of sulphate of ammonia on light, porous sands and gravels, and especially if lime is known to be abundant. Moreover, _ such soils, being well aerated, offer conditions favourable to the nitrification of the ammonia, and thus encourage its early use by plants. On the other hand, nitrate of soda is better adapted for strong land, where the dangers 116 ~ AGRICULTURE of loss by washing are at a minimum, and where the conditions for nitrification are, as a rule, not wholly satisfactory. On account of its attracting water from the air, the continued use of nitrate of soda in large quantities upon strong clay may result in the soil getting into bad mechanical condition, but this result is unlikely to attend the use of nitrate of soda in ordinary agricultural practice. The experiments at Rothamsted and Woburn have shown very conclusively that, — to give its best results, sulphate of ammonia must be used on soil containing a fairly high percentage of lime. At both these stations the annual use of ammoniacal salts has frequently resulted in great reduction of fertility ; in fact, at Woburn, the barley and wheat plots getting liberal annual dress- ings of this manure for over thirty-five years have long since become absolutely barren. — Chemical examination of the soil has shown that it is markedly acid, and that practically all the lime has been removed from it. This result has been produced by the acid of the ammoniacal manure entering into combination with the lime of the soil, the latter being removed in the form of soluble calcium salts. That this explanation is satisfactory appears to be confirmed by the fact, that when a PRINCIPLES OF MANURING 117 _ eomparatively small amount of lime was _ added to soil that had been brought into this ' condition, fertility was immediately restored ' and satisfactory yields were obtained. Sul- is phate of ammonia, therefore, would appear _ to be specially adapted for use upon chalky ' soils, and others derived from rocks contain- - ing a high percentage of lime. ' Climate also is not without influence in _ determining the special suitability of one or - other of these two manures. On account of the ease with which rain water removes ‘nitrate of soda from soil, one should rather hesitate to use it in a district of high rain- fall, or, at all events, other things being equal, preference would be given to the other . manure. Conversely, nitrate of soda would _ appear to have an advantage over sulphate | of ammonia m the drier districts of the East | and South of England, and especially if the soil is heavy. But after giving full consideration to these various questions, a farmer may still be in | doubt as to which manure to employ, and _ in the end his choice will probably be deter- — _ mined by considerations of cost. When the | two manurial substances under consideration are of standard quality, sulphate of ammonia, as compared with nitrate of soda, contains 118 AGRICULTURE nitrogen in the proportion of about 100 to 75, so that the former manure stands practically always at a higher price per ton than the latter. The basis of purity in the case of nitrate of soda is generally 95 per cent., whereas sulphate of ammonia ean usually be purchased under guarantee of 97 per cent. of purity. With these figures before us, it is easy to calculate what the relative amounts of nitrogen are in the two manures. Nitrate of soda when pure is a chemical substance, of which every 85 lb. contain 23 lb. of sodium, 14 lb. of nitrogen, and 48 Ib. of oxygen. Of these three substances it is only the nitrogen that interests us in the present connection, and if 85 lb. of nitrate of soda contain 14 Ib. of nitrogen, 95 lb. will contain 15°6 lb. Seeing _ that nitrate of soda is generally purchased on a basis of 95 per cent. of purity, it means that 100 lb. of this manure, as commercially obtainable, hold 15°6 lb. of nitrogen. It therefore follows that if 100 lb. of com- mercial nitrate of soda contain 15°6 lb. of nitrogen, a ton will hold 350 Ib. At the present time, nitrate of soda costs about £10 per ton, so that the 350 lb. of nitrogen which the ton contains are being purchased upon a basis of 6°9 pence per lb. PRINCIPLES OF MANURING 119 | Be Sulphate of ammonia is a substance of ' which, when pure, every 182 Ib. contain Me 9% ib. nitrogen, 8 b>: hydrogen; $2 .1b. _ sulphur, and 64 Ib. oxygen. But, like ' nitrate of soda, this substance is not used ' for manurial purposes in a _ chemically pure condition, the degree of purity being 3 usually $7 per cent. By calculation ' we find that if 132 Ib. of pure sulphate of - ammonia contain 28 Ib. of nitrogen, 97 lb. will contain 20°6 lb. Seeing that 97 per cent. of purity is the basis upon which we - usually purchase this manure, it follows that the percentage of nitrogen in ordinary com- mercial sulphate of ammonia is 20°6. From this it can be calculated that a ton of com- mercial sulphate of ammonia contains rather over 461 lb. of nitrogen, and at present the price is about £12 per ton. On this: basis it will be found that the price per pound of nitrogen in sulphate of ammonia is 6°3 pence, as contrasted with 6°9 pence in the ease of the nitrate of soda. At the prices we have ' assumed, therefore, sulphate of ammonia is t better value than nitrate of soda to the | extent of rather over 4d. per lb.; and if, in other respects, it is a matter of indifference which substance we employ, we should un- __ hesitatingly give the preference to the former, 120 AGRICULTURE In ordinary commercial practice in this country, these and similar nitrogenous manures are generally valued not on the basis of so much per pound of nitrogen, but by what is called the system of units. As illustrating this system we may take the two manures under consideration and adhere to the prices of £10 and £12 per ton re- spectively. To find the value per unit of nitrogen in the case of the nitrate of soda we divide the price per ton (£10) by the percentage of nitrogen (15°6), and the result is 12°82 shillings—say 12s. 10d. Similarly treating the sulphate of ammonia, we divide £12 by 20°6, when we find that the value of a unit of nitrogen is 11°65 shillings—say lls. 8d. There is therefore a difference of Is. 2d. per unit of nitrogen in favour of the sulphate of ammonia. Multiplying 20°6 by ls. 2d. we get £1, 4s., which, when added to £12, gives us the price per ton; £18, 4s., at which we might purchase sulphate of ammonia, and still get as good value as is represented by nitrate of soda at £10 per ton. Qr, we get at the same result if we multiply 20°6 by 12s. 10d.=£13, 4s., and from this deduct £12=£1, 4s., and the latter is the usual way of making the com- parative calculation. On the other hand, SPL LITELTE MED BBY ai x SS Ws "ie tig PRINCIPLES OF MANURING 121 _ with sulphate of ammonia at £12 per ton, _ that is 11s. 8d. per unit of nitrogen, we find, _ by multiplying 15°6 by 11s. 8d., that the _ corresponding price for nitrate of soda is @ £9, 2s. per ton. It was at one time common to speak of ' nitrogen and ammonia almost as if they were _ interchangeable terms. Merchants, too, often » stated the percentage of their manures both 2 : in terms of nitrogen and ammonia, and sometimes even in terms of ammonia only. This was frequently done in order to attract the eye of a possible buyer with a larger _ figure, the relationship between nitrogen and " ammonia being as 14 is to 17. In other ' words, 17 Ib. of ammonia consist of 14 lb. of nitrogen chemically combined with 3 lb. of hydrogen; so that, for instance, the : _ statement that a manure holds 8°5 per cent. of ammonia, is no better than saying that it holds 7 per cent of nitrogen. It is now, however, illegal to omit to state the per- centage of nitrogen, if any, in the invoice that must accompany the delivery of a manure. Valuation by units is a rapid and useful ‘method by which farmers may estimate | whether manures that are offered to them | are cheap or dear. Some Agricultural 122 - AGRICULTURE Societies issue annually to their members, usually in spring, a statement of the unit values of standard manurial substances. By means of these units, or of others which the farmer can readily work out for himself, it is. easy to ascertain whether manures that are offered are worth the money demanded or not. If, for instance, in any one year standard nitrate of soda containing about 154 per cent. of nitrogen has a unit value of 12s., that would mean that the price of a ton should be £9, 6s. Supposing that another sample of nitrate of soda were offered con- taining only 14 per cent. of nitrogen, the corresponding value per ton would be £8, 8s.; but having regard to the fact that the lower the quality the relatively — higher is the cost of carriage, it must be said that £8, 8s. is rather too high a price to pay for the lower-quality manure. Certainly if more than this price is demanded —as is most likely, for poor manures are seldom cheap—it is relatively dearer than the other at £9, 6s. If, on the other hand, it can be purchased much below £8, 8s., then it is relatively the better value. | If, after considering the various factors _ that determine one’s choice of a nitrogenous manure, the farmer has still a difficulty in ‘ _ PRINCIPLES OF MANURING 128 c ciding whether to use nitrate of soda or u Sehate of ammonia, he cannot do better = apply both, either separately or’ in ‘mixture. Field experiments have shown conclusively that on the average of soils and ‘seasons one will usually get a larger crop by applying half dressings of both nitrate of , oda and sulphate of ammonia to the same " area of land, than by using only one or other _ of these two substances. The gain in yield “may not be striking, but, in the case of the ’ turnip crop, for instance, it may amount » to as much as a ton per acre, and the value "of this weight of roots is much more than " sufficient to compensate for the extra labour - of mixing the two manurial substances. ' Sometimes, indeed, the crop given by the | mixture will be greater than the crops } grown by either of the two substances used | alone. The reason of the superior action ' of the mixture would appear to be that it || furnishes two kinds of nitrogen, one of which eects quickly, and the other more slowly. _The former, therefore, nourishes the crop in the early part of the season, while the latter _ becomes operative somewhat later, at a time, namely, when the effects of the other are on the wane. os late years considerable attention has ~ 124 = AGRICULTURE been given to the two new nitrogenous manures, Calcium Cyanamide or Nitrolim, and Nitrate of Lime. Both are produced by bringing the free nitrogen of the atmos- phere into chemical combination; nitrolim, as a result of decomposition in the soil, _ furnishing plants with ammonia, while nitrate _ of lime, of course, supplies nitrate nitrogen. Experiments seem to show that these two manures may be used for practically all purposes that are now served by the old standard nitrogenous manures, and so far as — yield of crop is concerned there seems very little to choose between them, where equal quantities of nitrogen areemployed. Calcium cyanamide is rather a dusty substance, and — therefore somewhat troublesome to sow, but’ this difficulty can be readily got over in © various ways, such as damping, or mixing © with superphosphate. It generally contains about 18 per cent. of nitrogen, that is to say its composition approaches that of sul- phate of ammonia; while nitrate of lime holds about 13 per cent. of nitrogen, a com- position somewhat below that of nitrate of soda. They may be valued, for com- mercial purposes, on the prices current per — unit of nitrogen in sulphate of ammonia | and nitrate of soda _ respectively. While PHOSPHATIC MANURES 125 4 experimental evidence goes to show that there is little difference in the effects of the _ two new substances, preference may on the _ whole be given to nitrate of lime, which, being _ anatural plant food, is at once available for _ the use of crops. ' As regards such a source of nitrogen as ' Rape Meal or Dried Blood, it may be said | that, as a rule, the unit value on the market is much too high; and, moreover, the nitrogen content (about 5 per cent. in the | case of Rape Meal) is so low that the cost _ of carriage and carting is relatively high. | - The nitrogen, too, is in the organic form, and slower in its action than any of the } four nitrogenous manures mentioned above. } ‘The circumstances must be very rare where a farmer would be justified in purchasing rape meal or dried blood as a source of nitrogen. = x i. CHAPTER VI » PHOSPHATIC, PHOSPHATIC-NITROGENOUS, AND POTASSIC MANURES _ Comine now to a second group of artificial | fertilizers, we may consider the leading forms 126 AGRICULTURE of purely phosphatic manures, of which by far the most important are Superphosphate — of Lime and Basic Slag. The former is obtained by treating ground phosphatic rock with sulphuric acid, during which process most of the raw insoluble phosphate is converted into a form soluble in water. In former times superphosphate was frequently put on the market in somewhat poor mechani- cal condition, a state of things due partly to the character of the rock phosphate employed, and partly to defective manufacture. Of late years, however, manufacturing details have been more carefully attended to, and the mechanical condition of superphosphate now seldom leaves anything to be desired. Basic slag, which has come into such — general use during the last twenty years, is a bye-product in the manufacture of steel from pig-iron, which contains considerable quantities of phosphorus. In the manu- facture of steel it is desirable to get rid of the phosphorus, and this is effected in a con- verter by blowing air through the molten iron mixed with lime until all the phosphorus is oxidized to phosphoric acid, which isthen _ withdrawn as a phosphate of lime in the slag that forms on the surface of the molten mass, and in the hme bricks which line the walls PHOSPHATIC MANURES 127, _ of the converter. The slag and bricks are _ subsequently ground into an impalpable _ powder, which is the material the farmer _ purchases and applies to his land as a phos- ' phatic manure. As in the case of nitrate ' of soda and sulphate of ammonia so here, ' a farmer has to weigh very carefully the ' advantages and disadvantages of purchasing _ basic slag as compared with superphosphate ' of lime. There is little doubt that super- ' phosphate, containing as it does soluble _ phosphate, is more rapid in its action than basie slag, and, consequently, for immediate _- effect, the former manure is to be preferred. _ But any objection to basic slag on the score } of slowness of action can be overcome to a | large extent by looking ahead; so that if | it is desired, for instance, to dress a root crop | with basic slag it can be applied to the land | some months before the time when the crop } will occupy the ground. During this interval | the insoluble phosphate of the slag will be | acted upon by the natural solvents of the soil, } so that a considerable proportion of the |. phosphoric acid will be immediately available | when the plants require it. | Except from the point of view of rapidity | of effect, basic slag would appear to possess ie advantages that are superior to those associ-. 128 AGRICULTURE ated with superphosphate. Basic slag is pre-eminently adapted for use upon grass land, and especially on land that has for some years been under pasture. Probably one reason why basic slag is capable of exerting its best effects on old grass land is that under such circumstances the soil contains a consider- able amount of humic and carbonic acids, which are formed during the decomposition of the vegetable matter. These weak acids react upon the slag, and appear to be sufficient to make a large proportion of the phosphate immediately available for the use of plants. While basic slag generally produces superior effects on grass land, it must be said that its action is most of all emphasized where there is any tendency towards sourness in the soil. — This condition of things is indicated by the presence of certain plants, such as Bent Grass, and more particularly the so-called Carnation Grass (Carex glauca). Whereas superphos- phate, being an acid substance, increases the acidity of soil, basic slag, being alkaline, tends to counteract acidity, and this action is to the advantage of all crops. ; It is often asserted that basic slag has little _ effect on grass land where the soil is sandy | or gravelly, or even where there is a marked tendency in this direction. Under these PHOSPHATIC MANURES 129 circumstances superphosphate would also _ produce little effect, and the reason in both eases is, not that the physical conditions of the soil are unsuitable for the action of the ‘manures, but that on light, gravelly soil the growth of White Clover cannot be markedly stimulated. Unless this plant can be induced to grow luxuriantly, at least in the earlier years of the renovation of a pasture, the final and permanent improvement that is our object will not be secured. It is a matter of common observation that White Clover grows best upon land that is well-consolidated. Why this should be so may not be clear, but at least there is nothing strange in a plant making very specific demands as to the character of the habitat in which alone it will grow well. Such pronounced peculi- arities are well known amongst garden flowers, and growers, to be successful, must _ take great pains to provide the right conditions } of soil and moisture. On fields which possess _ ni at ne es soil of an open texture it may be found that White Clover is abundant only along the side |. of a footpath that may cross the field, or in the neighbourhood of a gate round which stock have a tendency to congregate. In both cases the ground has been consolidated by treading, and thereby the conditions have ef | ‘180 - AGRICULTURE been improved for the growth of this par- ticular plant. But. throughout the body of the field there may be little evidence of the presence of White Clover, and under these circumstances the use of a phosphatic manure would probably produce little effect. UH, however, the land is well-consolidated— and this is the state of things im clay and clay loam—White Clover appears to find conditions thoroughly congenial to its growth, provided it can secure the necessary amount of phosphatic nourishment. We may walk across an unimproved field of this character and with difficulty find any considerable number of plants of White Clover. Some would say that none are present; but careful . observation will, as a rule, detect the presence of more plants than are at first obvious, but the plants are so small and starved that they frequently consist. of no more than two or three leaves, and. only rarely are they suffi- ciently strong to produce a flower. When, however, basic slag or superphosphate is applied to such land the results are often : little short of marvellous. In the first year | after the application of the fertilizer no great change may be visible, although im respect of this much depends upon the season. If the weather is very dry, the first year may PHOSPHATIC MANURES Is _ pass without any appreciable results being obtained ; on the other hand, if the summer is genial and sufficiently moist the phosphatic manure will have asserted itself long before the growing season is over. But it is in the second and subsequent ‘seasons that. the _ transformation is so striking. Land which was almost barren, and of a rental value of only a few shillings per-acre, has, by the use of basic slag or superphosphate, been trans- formed into a pasture so rich as to be capable of fattening stock, and of commanding a _ rent of more than a pound per acre. Although the prime factor in such im- provement is wild White Clover, it sometimes happens that almost as good results are obtained where the leguminous plants naturally present in the land are Trefoil (Medicago lupulina), or Bird’s-foot Trefoil _ (Lotus corniculatus), or Kidney Vetch (An- thyllis vulneraria), or Red Clover (Trifoliwm _ pratense). In the great majority of cases, however, the plant that is stimulated by _ the phosphatic manure is White Clover, and it is hardly too much to say that without the presence of this plant the striking results obtained by phosphatic manures on. grass land could not be secured. In this connec- tion it may be said that it seldom matters: E 2 132 AGRICULTURE whether basic slag or superphosphate of lime be used, but if basic slag does not succeed, there must be few cases where a_ better result would attend the use of the other substance. The course of the history of a pasture field which is improved by phosphatic dressings may be thus described. In the first year little result, if any, may be obtained, in the second year the effects are usually very striking, and in the third year they are equally so or even better. At this stage, in the month of July, the herbage may appear to consist of little but clover, which probably, if it-be sorted out and weighed, constitutes about 50 per cent. of the whole. From the third or fourth year onwards a change comes over the character of the herbage. White Clover, and leguminous plants gener- ally, become relatively scarcer, their place being taken by a stronger growth of grass. The grass, however, which supplants the White Clover is much superior, as a rule, to what the latter had previously displaced in the second and third years. On the kind of land where phosphatic manures produce their greatest effect, the commonest plant is usually Bent Grass, that is to say, some species or variety of Agrostis. This grass is } ' j f f r PHOSPHATIC MANURES 133 not appreciated by stock, which will hardly eat it,—at least during summer,—if better herbage is to be obtained. It is, to a large extent, suppressed by the luxuriant growth of clover which follows the use of phosphatie manure; but when the clover is in its turn partially displaced, the grasses that follow are generally Poas, Fescues, Fox-tail, Yellow Oat Grass, and Cock’s-foot. While grasses become more conspicuous about the fourth year, and tend to increase in subsequent years, White Clover does not by any means completely disappear, although it is usually much less abundant than in the earlier stages of the improvement. The cause of the reduction in quantity of the clover would appear to be associated ‘in some way with the phenomenon that is known as Clover Sickness, which, as is well known, prevents the growth of Red Clover, except at considerable intervals, on many classes of tillage land. While the causes of - Clover Sickness are not fully understood, it would appear to be likely that some re- stricting factor is induced to assert itself in consequence of the too frequent or over- luxuriant growth of clover; and one way by which the trouble may be overcome is to desist from the attempt to cultivate Red 134 -- AGRICULTURE | Clover on the particular field until the land has had a “rest.’” Many leguminous plants are subject to some such “sickness,” and: as alb must. have healthy colonies of bacteria on their roots for successful growth, the conclusion would appear to be justified that. the sickness of the plant is closely associated” with sickness amongst the bacteria. What- ever the reason, there is no doubt/as to the fact that White Clover, which may have been very abundant two or three years after phosphates were applied, becomes com paratively scarce. But after the clover has remained on a lower level of productive ness for some years, it generally responds to a repeated dressing of basic slag, although not to the same extent as in the first instance ; so that the most rational method of treating” such land would appear to be to apply a substantial dressing (7-10 cwt. per acre) of a phosphatie manure to begin with, and to supplement this after an interval of five or six years with a smaller dressing (4-6 cwt. per acre). Although superphosphate of lime has a stimulating influence upon clover, it is rarely that one sees quite such striking results from the use of this substance as those which follow the: i gear of baste slag. ae oe ee Ss v. PHOSPHATIC MANURES 1385 While it is popularly supposed that basic slag is not superior to superphosphate on light soil under grass, it is probably not maintained that there is any difference in the effects of the two substances upon light land under cultivation. The great majority of field trials on roots have shown that there is little to choose as regards effect, where equal quantities of phosphoric acid are supplied in the two forms of basic slag and superphosphate of lime, provided the former be applied a month or two before the crop is + sown. Certainly where equal money value of these two substances has been the basis of comparison, the results in the case of root erops have generally been in favour of basic slag. At prices hitherto current for these two manures, one has been able for the same expenditure to obtain about one-third more phosphoric acid in the form of basic slag than in superphosphate of lime. So satis- factory has the former manure proved, that it would not be surprising had the price risen to a higher level. But old customs have great tenacity, and superphosphate of lime, having been used by farmers for three- quarters-of a century, has attained a position from which the other substance has experi- enced a difficulty in dislodging it. : 136 AGRICULTURE et The alkaline character of basic slag places it in a superior position for use on a cruci- ferous crop which it is intended to grow on land known to be affected by finger-and- toe. Experiments have shown that this disease is encouraged by acidity in the soil, and superphosphate cannot fail to increase acidity to’ a greater or less degree, whereas basic slag tends to counteract it. This prejudicial effect of the acidity of superphosphate is so generally recognized that a manure, known as Basic Superphos- phate, has been placed on the market, the main character of which is that, by the addition of lime in the process of manu- facture, the originally water-soluble phos- - phate has been rendered insoluble, while the acidity has been more than neutralized. The insoluble phosphate thus formed is known as ‘‘ reverted’? phosphate, which, although insoluble in water, is soluble in a 2 per cent. solution of citric acid, and is therefore on equal terms of “availability ’? with the phosphate of basic slag. The acid character of superphosphate can also be neutralized by mixing this sub- | stance with basic slag, and experiments have shown that such a mixture gives excellent results. It may be adopted with advantage Sapient a ear ate PLES PHOSPHATIC MANURES 187° where one has a difficulty in deciding which of these two manures to use alone. The two substances just described are the most important of the purely phosphatic manures. A third, namely, Precipitated _ Phosphate, has given an excellent account of itself in field trials, but home supplies seem - to be so firmly held for export to Japan, Honolulu, the Mauritius, etc., that little is available for the British farmer. It is chiefly a bye-product in the manufacture of gelatine, glue, and similar substances from ‘ bones, the phosphate of which is rendered soluble by acid and subsequently precipitated by the addition of lime. Raw Muineral Phosphate, too, ground to a fine powder, has been employed with fair success on sour meadows, but the bulk of this substance is not used as manure till it has been made into superphosphate. Bone Ash, again—a substance imported from South America, where bones are often used as fuel—supplies little but phosphate, and, when ground up, a certain amount comes on the market as manure. The valuation of phosphatic manures may proceed on one or other of the lines indicated when dealing with nitrogenous manures. On the Continent the system adopted is to 188 AGRICULTURE determine the quantity of phosphoric acid contained in 1000 kilograms, say a ton, of the substance to be valued ; and, knowing the price per ton, one arrives at the cost per pound. This system may be illustrated by taking the case of basic slag, which is put on the market of different qualities, the phos- phorie acid usually varying between 10 and 20 per cent., corresponding to a percentage of phosphates of about 22 to 44. A common type of basic slag is one that holds 37 to 42, say 40, per cent. of total phosphates, which corresponds to a percentage of phosphoric acid of 18°32. The relationship between phosphoric acid and total phosphates may be explained as follows. The chemist, in analysing a phosphatic manure, determines the amount of phosphoric acid, and this, by calculation, he converts into tribasie caleic phosphate, the substance, namely, that is meant when one uses the shorter term ** phosphate ’”’ or “‘ phosphates.’’ The basis of the calculation is the chemical constitution. of tribasie -calcic phosphate, 310 Ib. of which contain 168 lb. of lime, united chemically with 142 lb. of phosphoric acid. If, therefore, 142 lb. of phosphoric acid can combine with 168 lb. of lime to form 310 1b. of ‘tribasic calcie phosphate, 18°32 lb. will PHOSPHATIC MANURES 1389 combine with the proportionate amount of lime to form®?40 lb. of tribasie calciec phos- 310 x 18°32 142 = 40. If 310 be divided by 142.-we get 2°2' (nearly), and this figure can be used as a multiplying factor to convert phosphoric acid into terms of phosphate; or as a dividing factor, in making the change from phosphate to phos- phorie acid. In the basic slag, therefore, that we have assumed, there is 18°82 per cent. of phosphoric acid, so that a ton. holds 410 lb. of this substance. Assuming that the basic slag costs £2, 10s. per ton, free on rail, this will mean that the phosphoric acid is being purchased at the rate of just under 14d. (really 1°46d:) per pound. It ‘is easy, therefore, to calculate what will be the price of a ton of any other quality that may be quoted at any particular rate per — of phosphoric acid. In this country, however, or less — unsatisfactory results. If, for any reason, | the distribution is unequal it must neces- | sarily follow that a certain proportion of — the field is over-manured, and other portions ‘correspondingly under-manured. Where too much manure has been applied the plants growing there may be destroyed by poisoning, . and especially will this be the case where a highly soluble manure like nitrate of soda is used, or an acid substance like super- phosphate of lime. When unequal distribu- © tion has not gone so far as to poison the | crop in places, it may result in the encourage- _ ment of excessive growth at certain spots, | ‘and correspondingly reduced growth at | others. Such a result would appear in its | most ‘undesirable form iin the case of the © barley crop, whose profits in many cases — ‘are dependent upon the securing of a ‘thoroughly equal sample of grain, and — THE USE OF MANURES 163! this cannot be obtained unless the crop is approximately of like vigour over the whole _ area, Where artificial manures:are employed on a considerable scale it will well. repay a: _ farmer to make an effort to secure a horse _ distributor of a thoroughly efficient type. _ Where artificial manures are sown by hand _ the work must be entrusted to. a thoroughly efficient worker. But even. the best worker, if he is asked to. apply something like a maximum dressing, is sure to attempt to over-fill his hand; with the result that as he removes the handful from the sowing sheet or seed-lip he is:sure to drop a certain | amount. before he begins: his: “‘ cast.’” Such | patchy work will subsequently become. } evident in a series of over-luxuriant spots } directly along the line that the worker has _ traversed, and one may depend upon it | that over luxuriance at these spots has been secured at the cost of reduced production on other parts of the ground. | Not only does patchy distribution result in over luxuriance at one place and reduced luxuriance in another, but it is also to be borne in mind that the heavier the dressing of manure the greater is the chance of loss by washing into the subsoil or into the drains. The absorptive power of: soil, that. F 2 164 AGRICULTURE is to say, its capacity to fix and retain in- gredients of plant food, is in inverse pro- portion to the quantity of soluble manure employed. The over-manuring, therefore, that results from patchy distribution must, at those points where excessive quantities have been applied, encourage waste of -manurial substances. Then, again, speaking generally, one wil obtain better results by applying, let us say, 20 ewt. of nitrate of soda to 20 acres, than © by applying the same quantity to 10 acres ~ and leaving the other 10 acres undressed; and similarly with regard to other manures — and other quantities. In all agricultural operations it is well to bear in mind the operation of what is called the Law of © Diminishing Returns. This law may be popularly expressed by saying that as one increases the dose of anything one does not. get a proportionate increase in the yield. | If, for instance, 1 cwt. of nitrate of soda | per acre results in an increase of 5 cwt. of | hay, 2 ewt. of nitrate of soda per acre will | not usually result in the production of 10 cwt., © but, of something less; and if one goes on — increasing the dose one will soon arrive at a point where the extra dressing will actually — bring about a decrease in the yield. | THE USE OF MANURES 165 Where a crop is top-dressed little can be done to incorporate the manure with the soil, but under other circumstances it is a good plan to work the manure into the land by means of the harrow or cultivator. The passage of these implements tends to improve the lateral distribution, and, at the same _ time, results in the manure being more com- _ pletely mixed up with the mass of soil. _ This helps the soil to fix it, and at the same time it is more completely appropriated by plant roots. The relationship between soil and manure should also be carefully con- sidered. Thus, other things being equal, _ sulphate of ammonia is preferable to nitrate of soda on light land. Basic slag has an _ advantage over superphosphate in the case - of peaty soil, whereas the reverse may be _ the case of chalky land. Potash, again, will _ have relatively more influence where the _ soil is sand or peat, than where it is clay. Enough has probably been said to empha- size the desirability of considering the rela- tionship of manures to crops. In the case of barley, for instance, which is a shallow- feeding plant, sulphate of ammonia is rela- tively of more importance than nitrate of soda, whereas in the case of mangolds the reverse holds true. In the treatment of 166. AGRICULTURE permanent meadow land, nitrate of soda is found to encourage deep-rooted. plants which, for the most. part, are of a better type, and more resistant. to drought, than shallow-rooted plants, like Smooth-stalked. Meadow Grass | and. Fiorin,. which are encouraged by the use of sulphate of ammonia. Whilst both these — nitrogenous manures tend to repress the ~ growth of, leguminous plants, this is more marked in the presence of sulphate of ammonia than of nitrate of soda. Then,. again, the inter-action of manures on. each other should not be forgotten. Probably, every. farmer. now, knows that if sulphate. of ammonia or Peruvian guano be mixed with basic slag, the free lime of the ~ latter reacts upon the ammoniacal manure 7 and liberates ammonia, whose escape into — the atmosphere can be detected. by its characteristic smell. Superphosphate of lime or dissolved: bones freshly made, and contain- ing. some. free acid, will liberate a certain amount of nitrogen. if mixed with nitrate — of soda. Such a mixture, therefore, should — be at once applied to the land, and, if possible, — harrowed, in. It will also be found that a mixture of superphosphate and. kainit will — get into a smeary condition it if is allowed — to lie too long: unused, and especially will this: — THE USE OF MANURES 167 ‘be ‘the case under humid ‘conditions of the “atmosphere. A mixture ‘of basic slag and _ ‘kainit sometimes ‘sets ’ very hard, it should _ ‘therefore ‘be used without delay. Tt used “to be argued that basic slag and ‘super- _ ‘phosphate of lime should ‘not ‘be ‘mixed together, it being urged that the free ‘lime ef the basic slag reacted ‘upon the soluble _ phosphate of the other ‘manure and caused it “to “revert” ‘to ‘an ‘insoluble ‘condition. This, no doubt, is true, but ‘it is ‘doubtful _ whether reverted phosphate ‘is essentially “of less value than ‘water-soluble phosphate, _ and in any ‘case the mixing of 'basic slag with ‘superphosphate, or with ‘dissolved bones, will tend to counteract the acid character _ of these manures; and for certain purposes, “notably for use on the ‘turnip crop, ‘where _ ‘finger-and-toe’is to be feared, the ‘neutraliza- tion of the acidity is an undoubted advantage. The many field trials carried out during the last twenty years by Agricultural Colleges, ‘and for a much longer period ‘by ‘the leading Agricultural ‘Societies, have shown con- -clusively that farmers should not depend ‘too implicitly upon ‘general principles ‘with ‘regard to the use ‘of artificial manures, but ‘should take steps to ascertain the particular “requirements of their own farms. This can 168 AGRICULTURE easily be done, and, it may be added, only be done through the agency of properly con- ducted field experiments. Such experiments are not difficult to arrange, nor do they involve a great deal of outlay, but to secure the greatest amount of information, with the minimum amount of trouble and expense, — they must be laid down on a well-thought-out ~ scheme. Land of approximately equal char- — acter must be made use of, and the plots © should be laid down at a sufficient distance from such disturbing agencies as hedgerows, ~ plantations, or isolated trees. They must © also be accurately measured, and, later on, ~ the crop should be carefully weighed. In the © case of permanent grass land the shape of © the plot is not a matter of much importance, © but where one is dealing with root crops it is convenient that each plot shall be oblong in shape, say 60 yards in length*and 4, or © more, in width, the total area of each plot | being not less than ~,th acre. By proceeding upon a well-considered plan, © one will get the maximum amount of informa- | tion from the minimum number of plots. If, for instance, it is desired to ascertain whether, on some particular type of soil, nitrogen, _ phosphates and potash are allfrequired for the treatment of the turnip crop, and, further- | THE USE OF MANURES 169 more, if information is wanted with regard to the actual quantities of these substances that should be employed per acre, one would proceed on some such scheme as this :— Plot 1. No manure. Plot 2. 5 cwt. super., 1 cwt. nitrate of soda, 5 ewt. kainit. Plot 3. No super., 1 ewt. nitrate of soda, 5 ewt. kainit. Plot 4. 5 ewt. super., no nitrate of soda, 5 ewt. kainit. : Plot 5. 5 ewt. super., 1 cwt. nitrate of soda, no kainit. By comparing the results on plots 2 and 8, one will ascertain the effects of superphos- phate ; by comparing plots 2 and 4 the effects _ of nitrate of soda will be seen; and, similarly, __ by comparing the results on plots 2 and 5 one will learn the effects of kainit. Where the ' turnip crop is concerned, one may almost assume that phosphate will be required, so that plot 3 might be omitted. It might also similarly be assumed, that a certain amount of nitrogen will be wanted, in which ease plot 4 would be dropped from the scheme. But as it can never be assumed that some form of potash will or will not be required it will be necessary to retain plot 5. Simi- 170, AGRICULTURE larly, it might, be argued. that. plot No. 1, recciving no. manure, is unnecessary; but, as the yield of this. plot. will prove interesting as throwing light. upon the natural capa- bilities of the soil, it is perhaps on the whole desirable to have an unmanured plot. This simple five-plot test may be extended almost indefinitely, and certainly in the majority of cases it should be supplemented by additional plots. For instance, it is probably desirable to: ascertain what is the profitable limit. of the use of a phosphatic manure, and for this purpose- a sixth plot could be laid down, receiving 74 ewt. of superphosphate along. with the nitrate of soda and. kainit of plot 2.. By so.doing-we have the opportunity _ of ascertaining (a)-the effects of the omission. altogether of superphosphate (compare plots. 2 and 3), and, (b) the effects. of a: moderate: © as compared with a large dressing of super- phosphate (compare. plots, 8, 2, and 6). Of course a. still larger dose of superphosphate. could be: tried upon an additional plot, but, for ordinary, practical, purposes, this. is per- haps.scarcely necessary. It. will, however, - be useful, in. many. cases, to; ascertain what. amount. of, nitrate of soda and kainit can. be profitably employed, and; for this. purpose: 4 we can add, the, following. plots :— RS Re ERD gh gE oh, THE USE OF MANURES 171 7. 5 ewt. super., 14 ewt. ‘nitrate of soda, 5 ewt. kainit. 8. 5 ewt. super., 2 cwt. nitrate of soda, 5 ewt. kainit. 9. 5 ewt. super., 1 cwt.’nitrate of soda, 74 ewt. kainit. 10. 5 ewt.'super., 1 cwt. nitrate of soda, 10 ewt. kainit. 3 By ‘comparing plots 4, 2, 7, and 8, in the order named, we get information with regard to the effects of increasing quantities of . Nitrate of soda; and similarly by comparing plots 5, 2, 9, and 10, in ‘the order given, information ‘will be forthcoming ‘with regard ‘to the profitable limit in the use’ of kainit. Instead of, or in addition to, ascertaining the most profitable quantity of these three “ingredients, we might—after plot 5, or after ey plot 10—proceed to put down additional ‘plots, with ‘the ‘object of discovering the “‘yelative effects of superphosphate and basic ‘slag, or of nitrate of soda and sulphate of ‘ammonia, or of kainit’and ‘muriate of potash. _ ‘fo ‘compare the relative effects of ‘super- _ ~phosphate and basic slag we could add a plot Teeeiving ‘basic slag, equal in monéy-value ‘to’5 cwt. superphosphate, and when this plot is compared with plot 2, the comparative 172 AGRICULTURE action of the two phosphatic substances will be indicated. Similarly, if we desire to compare the relative effects of nitrate of soda and sulphate of ammonia, a plot may be dressed with 5 cwt. super., # cwt. sulphate of ammonia, and 5 ewt. kainit, when a comparison of the yield of this plot, with that of plot 2, will give information as regards the relative action of these two nitrogenous manures. Similarly with regard to a com- parison of the effects of kainit and muriate of potash, 1 cwt. of the latter substance (90 per cent. pure) being about equivalent to 5 cwt. of the former. Even when every care has been exercised in selecting and measuring the land, and in applying the manures and weighing the crop, one series of plots, confined to a single season without any check, can hardly be expected to give thoroughly trustworthy information. The most reliable line to follow is to duplicate all the plots, and if it is found that there is marked consistency in the yields of the two series, the results may be taken as sufficiently reliable for ordinary practical purposes. But duplicating all the plots means doubling the expense, and, in order to keep down the cost, it will gener- ally be sufficient to duplicate certain of the ge a aa ae zee? oe Fes FARMYARD MANURE 173 plots only; so that if the yields from the plots that are duplicated do not deviate from each other by more than 10 per cent., the tests may be held to be sufficiently reliable. In the above scheme of experi- ments the plot that had best be repeated, once or oftener, is plot 2. In the five-plot test, therefore, we might have plot 2 (under the designation of 2A) repeated after plot 5, while in the larger scheme involving 10 plots, plot 2 might with advantage be repeated, not only after plot 5, but also after plot 10, when it would be designated as 2s. The Board of Agriculture have issued a pamphlet dealing with field experiments, and this should be obtained by those desirous of going further into the subject, especially on co-operative lines. CHAPTER VIII FARMYARD MANURE ALTHOUGH we have so far confined our atten- tion to artificial manures, farmyard manure is really of greater importance than any, for the reason that practically every farmer 1t4 - AGRICULTURE is called upon to ‘deal ‘with this ‘substance. Farmyard manure is ‘a substance of very indefinite ‘composition, depending as it does © for sits quality and character upon the food that the animals consume, upon the litter with which they are bedded, and upon the ‘way in which the substance is stored and handled. Speaking generally, it contains about 75 percent. of ‘water and 25 per cent. of dry matter. The fertilizing ingredients are, of course, entirely confined to the dry material, which holds ‘nitrogen—usually about one-half per -cent. of the total weight of amanure—and mineral matter. The latter is the so-called “ ash’ of the chemist, and contains ‘the phosphates, potash, lime, mag- nesia, and other mineral substances which serve as plant food. Phosphoric acid is usually present to the extent of about one- fifth per cent., while potash and lime amount to about one-half per cent. A ton of farm- yard manure will, therefore, contain about 12 lb. of nitrogen, a similar amount of potash, and 4 to 5.db..of phosphoric acid. From the point of view of plant nutrition, we can, oi course, obtain these substances from other sources. Thus we might © purchase commercial «nitrate of soda to ssupply the nitrogen, 77 Ib. of that substance being Sed che eer to ee al aa a FARMYARD MANURE 175: a required to furnish 12 lb. of nitrogen, and, _ assuming the price of the nitrate of soda _ to be £10 per ton, the outlay on 77 lb. would be 6s. 10d. Similarly, to obtain: 12: Ib. of potash we might purchase 100 |b. of kainit - at a cost of about 2s.; and.to obtain 5 lb, _ phosphoric acid we might select a 30-per-. - cent.-seluble superphosphate. costing: £2,. 15s. - a ton, of which 87 lb: would be necessary, - involving: an outlay of Id. Adding these: _ figures. together, we obtain a_ theoretical value for farmyard manure of: 9s. 9d. per ton, a sum that is much in excess of: its: ‘market price. In point of. fact; certain con-. siderations combine greatly to reduce: the value of farmyard: manure below: its theo- retical level: Thus) it has been found: at _ Rothamsted that only one-fourth to one-third _ of the nitrogen supplied, in farmyard manure is utilized by plants, as. contrasted with _ three-fourths in the case of the nitrogen of nitrate of soda. If the fate of the phosphoric acid and: potash could: thus be followed up, it; would: probably be: found that their availability in farmyard manure is no greater _ than: that: of the nitrogen. Then, again. farmyard manure:is a very dilute: substance; so that large quantities have: to be applicd: to. the: land to: secure a full. crop, and: the: 176 AGRICULTURE handling of 10 to 20 tons per acre involves heavy outlay on horse and manual labour. Against this, however, is to be set the fact that farmyard manure greatly improves land, apart altogether from the manurial elements that it supplies. Following the indications given at Rothamsted with regard to the relative value of the nitrogen, we should probably reach a juster estimate of the value — of farmyard manure if we divide its theo- retical value by two, and take about 5s. per ton as its full practical value—a price, including carriage, that many farmers and market gardeners are prepared to pay. When a farm animal consumes an ordinary ration it is found that for every 100 lb. of dry matter in the food about 50 lb. reappear, the difference, namely, one-half, taking the form of water and gas in the process of digestion, while a small quantity may be stored up in the form of animal tissue (bone, muscie, fat, hair, etc.). It is possible to make a calculation of some service for practical purposes, as to the amount of farmyard manure that may be expected from a certain number of animals consuming a normal quantity of food, and being bedded in the ordinary fashion. A well-grown cow or steer, weighing 8 or 9 ewt., - FARMYARD MANURE 177 may be kept on some such daily ration as this: 4% ewt. roots, 8 lb. mixed cake and meal, and a stone of hay or straw. The percentage of dry matter in the roots may be taken as 10, while the corresponding figure for the other food may be put at 86. On this basis it will be found that the animal daily consumes about 24 lb. of absolutely dry food, and will, in addition, require daily at least 6 lb. of straw, calculated dry, as litter. Of the 24 lb. of dry matter consumed as food about one-half will reappear in the dung and urine, while the whole of the litter will be converted into the farmyard manure. We have thus to deal with 18 lb. of perfectly dry substance that daily finds its way to the manure heap. If ordinary farmyard manure contains 75 per cent. of _ water, we must multiply the 18 by 4 in order to get the daily output of farmyard manure, in the condition in which we find it in the manure heap. Assuming that the farm animals are under cover for six months of the year, this means that an ordinary well-grown cow or steer will con- tribute between 5 and 6 tons of manure to the general supply. During the time of storage, which on the average may be put at about three months, the farmyard manure 178. AGRICULTURE will, as a:result of fermentation, lose about 20 per cent. of its organic matter; so that in.order to ascertain the approximate quantity that: will be available for distribution: to the land, we must reduce the weight of fresh: dung: by: one-fifth. One may also make a useful estimate of the: probable: output. of farmyard: manure if one has: am approximately accurate idea of the amount of straw at: the farmer’s. disposal for feeding to cattle: and: for use as litter: It is usually assumed: that for each ton. of straw consumed at the homestead about 3: tons of farmyard manure: should later be available. Suppose the: case ‘of a farm of 200° acres which is worked upon: the four- course: shift, and: where; therefore, of the whole tillage area, one-half (100 acres) is under corn: crops; and! one-fourth (50 acres) under roots. Such a farm. will. produce about 120;tons;of straw, equivalent: to about 360: tons: of farmyard. manure, and if this is distributed: equally over half: the root. break the land: will receive about 15 tons: of dung per acre, which is approximately what: farmers, usually expect im practice. This relationship of 1 ton. of straw to 3 tons of: farmyard manure is: also taken as the basis: of calculation, when: straw is: sold off: FARMYARD MANURE 179 _ ‘a farm, as to how much farmyard manure _ should be brought back to the holding, so that its fertility may be maintained. ‘Of the constituents of the food, the most important, from the point of ‘view of manur- ing, is the nitrogen, of which, in the case of fattening cattle, about 96\per cent. reappears in the form of fertilizing material, ‘some ‘23 .. per cent. being in the solid form in the dung, and about 73 ‘per ‘cent. in solution in the urine. The balance, namely 4 per cent., is stored up in the animal’s tissues in ‘the form of ‘hair, flesh and bone.. The nitrogen of the urine ‘is by ‘far the most active and valuable, hence the reason that it is ‘so desirable to prevent the loss of liquids. In the ease of a milk cow, however, where milk is sold off the farm, only about 75 ,per cent. of the nitrogen reappears in the manure, a large proportion of the balance finding its way into the milk in the form of casein and albumen. In the case of growing animals, ‘also, a smaller proportion of the nitrogen will reappear in ‘the excreta, though the ~proportion so returned is greater than in the ‘case of milk ‘cows. As regards the phosphates and potash, a very small quantity ‘is retained even by ‘animals increasing in ‘weight, more, however, by young growing, 180 AGRICULTURE than by mature fattening beasts, so that nearly all becomes available for the use of crops. The larger proportion of the potash appears in the urine, while the most of the phosphates are voided as undigested residues in the dung. It is possible by means of a calculation to indicate the difference in the quality and value of farmyard manure produced in the one case by fattening steers and in the other case by milk cows. In the case of a cow yielding 700 gallons of milk in the course of the year, the following approximate quantities of fertilizing materials will be removed from the food and diverted to the milk :— £8. & 42 lb. of nitrogen at 64d. per Ib. +e hae 16 lb. of phosphoric acid at 14d. perIb. 0 2 O 14 Ib, of potash at 2d. per lb. 0 2 4 Eis es Assuming that, the cow stands in a byre for half the year, producing during that time 6 tons of farmyard manure, the above figure would be reduced by one-half, which means that each ton of farmyard manure is dim- inished in value by about 2s. 3d. A steer weighing 7 to 9 ecwt., in passing from FARMYARD MANURE 181 the store to the fat condition, during a period of 6 months will increase about 320 lb. in live weight ; and this increase will contain about 3 lb. of nitrogen, 2 lb. of phos- phoric acid, and } lb. of potash. Valuing these substances as before, and similarly assuming an out-put of 6 tons of dung, we find that the theoretical difference in the value of a ton of farmyard manure made in the one case by a milk cow and in the other case by a fattening steer is about ls. 11d. In actual practice, however, the difference in value will probably be less, because during six months a milk cow will usually consume a larger quantity of nitrogenous food than a steer passing from the store to the fat condition, and the nitrogenous residues in the former case may also be greater. While the quality of farmyard manure is primarily influenced by the character of the food, it also depends to a large extent upon other causes. Thus, the various farm animals produce manure of differing char- acter and quality, that produced by bovine animals being comparatively wet and dense, so that the mass is not well permeated by air. As a consequence it decays slowly, being what farmers and gardeners call ‘‘ cold,’’ so that, when applied to the land, 482 AGRICULTURE it -decays slowly, and therefore its effects ‘are more lasting. ‘On the other ‘hand, ‘manure produced — ‘horses fed, as they are, on ‘drier food, con- tains less water, and -is not ‘so thoroughly disintegrated ; ‘the ‘result being that it is more porous, and being better permeated by air it ferments more rapidly, and is of if the ‘character ‘to which the term “hot ”’ is applied. It is, therefore, only manure furnished by stables that is utilized by gardeners as material for imparting heat to a forcing frame. But just because the manure of horses ferments so readily there is a greater risk of loss of nitrogen during ‘the time of storage. That nitrogen is more abundant ‘in the air of a stable than of a cowhouse is ‘evident from the ‘characteristic smell of ‘ammonia ‘which is associated with ‘Ul-ventilated ‘stables. ‘The manure furnished by piggeries ‘rather ‘resembles that produced by bovine animals, ‘though a good deal depends ‘upon the char- acter of the food supplied to the pigs, which, if sloppy in ‘character, ‘produces ‘a ‘cold, low- ‘class manure ; ‘whereas if the pigs are get- ting ‘large quantities of ‘such ’a substance as pea meal, the resultant manure may be comparatively rich. 4 Jz + 4 B " i —_ > 2 —aes ees ee eS FARMYARD MANURE 188; _ Seeing: that. farmyard manure can seldom - be-carted direct to the land, it is necessary to provide suitable conditions for storage during: a period of three months or more, The objects. during this period should be to secure the. preservation of the valuable ingredients, to produce. equality through- - out the mass,. and, to prevent excessive: reduction in weight. To secure. these. desir- - able results the following points. should be attended’ to. The: floor of the dung heap — should, as far as possible, be; impervious: to _ the passage of liquids, nor should liquids. be allowed to. flow away from the mass, unless they can be led into, a suitable tank. These liquids. contain most of the potash, and also. the larger percentage of.the nitrogen, and especially of the nitrogen that is. more immediately available for the use of. crops. One should: also see that fermentation pro-. ceeds slowly. and uniformly, an object. that: is best. secured by keeping the mass as com-. pact as possible, and by maintaining it in a thoroughly. moist condition. Compactness: can be best seeured. by making the heap: as; deep. as. possible, and by running: the barrow, that brings the manure from the various; houses, over. the heap, so.as,to-assist consoli-. dation, As. regards moisture, there will be = AGRICULTURE least difficulty where storage is done in the open air; but if the rainfall is low, and especially if the manure is stored under cover, it is well to have a tank into which the liquids can drain, and from which they may be periodically pumped and distributed over the mass of manure. Then, again, one should see that the manure from the various buildings—stables, cowhouses, and piggeries —is equally distributed over the heap, so that the dense, moist, cold manure from the cowhouses and piggeries shall have an oppor- tunity of doing something to counteract the tendency towards excessive fermentation that is inseparable from stable dung. If manure must be used when in a com- paratively fresh condition it is well to apply it, where possible, to the heaviest class of land, because such manure can do most to open up the soil, and encourage the circula- tion of air. If proper conditions of storage have been observed, the loss of weight in three months may amount to no more than 20 per cent.; but during a longer period of storage, and especially in the absence of satisfactory conditions, the loss may amount to quite 50 per cent. While loss of weight cannot be prevented under any circum- stances, there should be proportionately FARMYARD MANURE 185 less loss of plant food, and, as a conse- quence, well-decomposed farmyard manure is relatively richer in nitrogen, phosphoric acid and potash than manure which is comparatively fresh. Many attempts have been made to create conditions in the manure heap which will prevent undue loss in weight, and at the same time preserve the nitrogen as far as possible. Saturation with liquids is one way of arresting fermentation, and of pre- venting the escape of nitrogen, but with excessive moisture there is undoubtedly in- creased danger of loss by drainage. It has also been suggested that superphosphate, gypsum, kainit, and other substances, should be thinly sprinkled over the manure while it lies in the stalls and yards, or as it comes from the various houses, but it cannot be said that experiments in this direction have demonstrated results of much practical value. On the other hand, the spreading of a con- siderable amount of soil over the heap at _ frequent intervals, will do something to arrest the loss of ammonia, and prevent excessive decomposition. Good results, also, will attend the use of a certain proportion of moss litter along with straw bedding, the former having greater capacity for the “186 AGRICULTURE -‘ebsorption of liquids, combined ‘with ‘the ' ipower to fix ammonia. If a ‘considerable ‘amount of ‘moss litter is employed, the ‘resultant manure will be found to be better adapted for use on light ‘than ‘on ‘strong Jland, because its power of absorbing and retaining water reacts more beneficially ‘in ithe former case ‘than in the latter. In order ‘to ‘save cartage at a busy time 46f the year it is ‘a ‘common custom in many parts of the country to‘empty the dungstead once or oftener during winter, ‘and to store the material m temporary ‘heaps in ’the field. ‘The ‘process of removal from ‘the place ‘of storage at the homestead to the field heap means that ‘the manure is left comparatively loose, so that air enters freely, and volatiliza- ‘tion of ammonia, fermentation, and reduc- tion in weight must go on to‘a ‘greater extent ‘than. if no disturbance had ‘taken place. Possibly, also, the temporary ‘heap in the field may be ‘placed upon land that is by mo means impervious to the downward passage of liquids, ‘or it may be situated on a slope which encourages the escape of liquids over the ‘surface of the ground. Do what one will, ‘it’ is impossible to avoid very ‘considerable loss ‘from such temporary storage sheaps; and, ‘speaking generally, the practice FARMYARD MANURE 187 should not be resorted to unless obvious. _ advantages are to be obtained. But. if it _ is resolved to empty the dungstead, and to. _ form a temporary heap in the field, one ' should endeavour to secure in the shortest _ time as great compactness as possible; and: ' this object is gained most effectively by. ~ making what is called a ‘‘ draw ”’ heap, that _ is to. say a heap over which each load of | manure as it arrives from the homestead. is ' drawn or. carted. The passage of the carts - consolidates the mass inthe best possible way; --and, if subsequently the sloping ends are eut off, and the material thrown on to the ' top of the heap, much will be done to obviate ' loss and. produce good. material, In order further to consolidate the mass and exclude _ air, it is good practice to throw about a foot _ of soil on to the top of the mass. When farmyard manure is carted on to _ the land for the purpose of being spread, it should not be left to lie for a longer time | than is possible in the small heaps that are | iormed when it is dragged from the cart. | The practice that one sometimes sees of | leaving these small heaps unspread. for days, } and even for. weeks, cannot. be. too strongly ' condemned, for the reason that the liquids: | drain away and percolate into the soil on: 188 AGRICULTURE which the heaps rest, with the result that certain spots on the field are over-manured, while the bulk of the field receives a corre- spondingly smaller amount of fertilizing materials. The loss will necessarily be greatest should much rain fall before the heaps have been spread. Whenever farmyard manure has_ been spread over the surface of tillage land it ought to be ploughed in as quickly as pos- sible, because only when it is incorporated with the soil is the loss of ammonia by escape into the atmosphere reduced to a minimum. Moreover, many of the valuable physical effects that dung exerts on the soil cannot operate till the material is ploughed under. CHAPTER IX ROTATION OF CROPS WHENEVER agriculture has advanced be- yond primitive conditions one finds farmers alternating different crops on different areas, in place of growing one single crop-species on the same land year after year. The objects and advantages of a rotation of crops may be summarized as follows. — = + UU” -7 ee ee a seem te ts)S -- Se =e oa a ae Se eS % are BA ° = "7 So. ae Wes Be Fee ROTATION OF CROPS 189 Different crops have different systems of root development; in some, e.g. mangolds, the roots go deep into the soil, while in others, e.g. barley, the roots are disposed within comparatively few inches of the surface of the ground. If one were to grow only shallow-rooted crops, practically no use could be made of the plant food lying ' deep in the subsoil. On the other hand, if one confined one’s choice to deep-rooted crops, the plant food present in the surface soil would be insufficiently utilized. But by ‘ alternating, either annually or periodically, deep-rooted and shallow-rooted plants the whole body of soil is laid under contribution to provide nourishment, and not only so but plant food drawn from considerable depths by such a crop as mangolds or wheat, will, when the crop is consumed and the residues returned to the land as manure, become available for the use of such a shallow- rooted crop as barley. | While all crops make use of the same kind of plant food, their requirements in the matter of quantity vary within very wide limits. As regards nitrogen, we find that a crop of cereals or of potatoes removes from | the land only about 50 lb. per acre, whereas _ turnips and swedes require twice as much, 190. AGRICULTURE and mangolds three times as much of this element. Similarly as regards potash, wheat and barley removing only about 30 lb. per acre, whereas red clover and swedes to give a full yield must have two or three times: as much, and turnips about five times as much of this substance. The variations in the requirements of crops for phosphoric acid. are not quite so wide as in the case of the two nutritive materials already referred: to, but even here we find variations between a minimum of some 20 lb. per acre in the case of potatoes, swedes, red clover, and the cereals generally, and of: 50 lb. in the case of the mangold crop. If, therefore; one were to grow only a single crop on any field, one would have to manure very liberally with the particular ingredient that the crop specially affected, and at the same time one would. know that materials for which the crop had little use were likely to be going to waste. It is found that the residues of roots, stubble, and leaves, left’ in and on a field by the growth of a particular crop, prove ex- cellent plant food for another crop of a different species, whereas one would not often. find: that these residues sufficed to — grow a correspondingly large crop of. the Re Bee alls AR TAG BA wr ROTATION OF CROPS 191 Ppeaine species as had in ‘the previous year E occupied the field. When a crop oof ired _ clover is removed from the land, it is found _ that wheat thrives vigorously upon the _ idecaying roots of the clover; while ‘the leaves of the turnip crop that are left upon _ the land have a markedly beneficial effect mpon a crop of cereals that may follow. If _ any one doubts the fertilizing value ‘of _ turnip Jeaves one has only to look es ROTATION OF CROPS 197 holding, and let it revert to prairie con- ditions, or to introduce crops other than cereals, so that the maintenance of cattle may become possible. To the credit of a rational rotation must also be put comparative freedom from the attack of injurious insects. Most of our most destructive insects are very fastidious as regards the diet that they require, and are incapable of living upon any plant but the particular species, or at most genus, that they affect. Thus, for instance, the carrot fly is met with on no other crop; the turnip flea beetle is dependent for its existence upon the presence of cruciferous plants; the mangold fly can only exist in the leaves of beets and mangolds; while the Hessian fly confines its devastations entirely to the Gramines, and, one might almost say, entirely to cereals. A few insects are less specialized in their food requirements, as, for instance, the cockchafer grub, the larva of the daddy-long-legs, and the wire-worm. But, speaking generally, the first class contains the majority of our thoroughly destructive insects. In the case, then, of an insect, highly specialized as regards its nutriment, the farmer can do much to hold it in check by depriving it in alternate years, 198 ‘AGRICULTURE or over longer periods, of the aegpiapees food plant that it requires. It is a matter of observation that rotations vary in character to a greater or less extent in different parts of the country, and it is also found that even on the same farm ‘the rotation adopted may from time ‘to time undergo modifications. ‘The growing scarcity of agricultural labour has not been without influence in shaping rotations, the tendency | where labour is scarce, dear, or inefficient, being in the direction .of extending the proportion of land under cereals, and notably under grass. The same:result will be reached where a farm is situated inconveniently ‘to markets, because, under these cireumstances, there is a disposition on ‘the part of ‘the farmer to increase his head of stock, live animals being marketed -at Jess trouble and expense than dead produce, whieh requires to be carted to its destination. ‘Then, again, some land.takes “‘ kindly ” to grass, whereas in the case of other land the production of a satisfactory pasture is a matter of heavy outlay and long delay. ‘If, then, a farmer is dealing with land which can‘ be depended on to graze well under a system of three or ‘four years’ ley, he will be encouraged to:put more of his land: under pasture, than ROTATION OF CROPS 199 if good temporary leys are difficult’ to secure, In some districts conditions of soil and climate favour the growth of certain crops, or encourage certain systems of stock-keeping. Thus, with a moderate rainfall and heavy soil, the tendency is in the direction of putting a large area of the farm under wheat or beans. In other districts, barley-growing may be attractive, a system of farming which is usually closely associated with the cultiva- tion of turnips. Then, again, the whole system of cropping may be arranged with a view to keeping as large a head of sheep as possible; in another district dairying may be the principal object in view, and this necessitates the growth of large quantities of bulky fodder, and of abundant supplies of green food. The possibility or otherwise of making cleaning crops a regular feature of a rotation, has an important bearing upon the percentage of tillage land that must be bare-fallowed, for if a cleaning crop cannot _ be depended upon every four or five years, the land must, at some such interval, be left uncropped throughout a season to permit of the eradication of weeds. The occurrence of disease in certain crops often entails drastic modifications of a rotation. For 200 AGRICULTURE instance, if cruciferous crops recur upon the same land, even at intervals of four or five years, they are often so affected by the disease of finger-and-toe that it becomes necessary to make arrangements for a much wider interval between consecutive crops of this family. Red clover, too, often presents similar difficulties ; and leguminous crops generally, if they follow each other too closely, are found to contract some form of ‘‘sickness,’”? which in ordinary practice can best be circumvented by modifications in the rotation. The most primitive rotation, if indeed it merits such a term, is that which was practised under the old system of village communities that at one time prevailed in this country, and at a more recent period on the Con- tinent. Under this system the land was annually cropped with wheat, or some other cereal, receiving no manure beyond what was dropped by the flocks and herds which grazed on the stubbles during autumn and early winter. When the produce of the land deteriorated to such an extent as to return little beyond the seed, the cultivated area was abandoned and allowed to revert to weeds, which ultimately formed. a rough pasture; and as nothing was. withdrawn ROTATION OF CROPS 201 under such management, the land in the course of time regained a certain amount of fertility, and it became possible once more to put it through a course of cropping. One finds this system of agriculture prevalent over large areas of the North American Continent at the present time. In the west of the United States and of Canada, farmers _ are annually taking wheat crops off the recently reclaimed prairie, no farmyard manure whatever being given, in fact much of the straw is burned in the process of stoking the engine of the thrashing machine that annually visits the holding. For a longer or shorter series of years the crops obtained leave a more or less satisfactory margin of profit, but in the course of time the yield falls to such a low ebb that nothing remains to the cultivator after outgoings have been met. It then becomes necessary either to apply manure to the land or to abandon it. In the older districts of the United States and Canada, where an in- dustrial population has gathered in certain centres, farmers find that it is profitable to maintain stock for the production of meat or milk, and the presence of stock necessarily means the consumption as food and litter of large quantities of straw, with the con- 2022 AGRICULTURE eurrent production of farmyard manure. Farms which have been adapted to such conditions of management tend to regain fertility, and if artificial manures can also be applied, such land can be profitably farmed indefinitely. But in many parts of the eastern United States one finds wide areas which, at one time under cultivation, are now reverting to forest, the attractions of the virgin land of the West being too great for the farmers who have taken all they can get out of their eastern holdings. In the Middle Ages, and more recently— in fact, the system is still met with in certain districts of England—large areas of tillage land throughout Europe were managed upon the three-field rotation, or, as the Germans eall it, the ‘* Dreifelderwirtschaft,” under which the tillage area was equally divided between a winter cereal (wheat or rye), a spring cereal (barley or oats), and bare fallow. It was an improvement on this system to substitute beans for bare fallow, especially if the bean crop was taken ad- vantage of to practise summer cultivation for the suppression of weeds. As the number of crop-species increased it became possible still further to modify the three-field rotation, which might then take the form of— ROTATION OF CROPS 203 1. Wheat, or some other cereal. 2. Beans or clover, or peas. 3. Potatoes, cabbages, turnips, etc, In some parts of the Cambridge Fens one finds at the present day a three- -course rotation, consisting of— 1. Potatoes, mangolds, or mustard. 2. Wheat. 3. Oats. The introduction into this country, in the first half of the eighteenth century, of the turnip crop led farmers in the east of England to adopt what has come to be known as the Norfolk four-course shift or rotation. This rotation, with its modifications, is now the most important in Britain, and has also been largely adopted in various parts of Europe and America. The Norfolk rotation in its simplest form consists of— _ 1. Turnips or swedes, partly consumed on the land by sheep, and partly drawn to the homestead for cattle. 2. Barley. 3. Clover. 4. Wheat. But the rotation is essentially the same if mangolds: or potatoes are partly: substituted 204 AGRICULTURE for turnips, if oats or wheat partly take the place of barley, and if oats replace a certain proportion of wheat. The displace- ment of one-half of the turnip break by potatoes or mangolds is found to be desirable on land that is much addicted to finger-and- toe, so that, under this modification, instead of any field coming under turnips or swedes once in four years, a cruciferous crop would recur only at intervals of eight years. If care be taken not to reinfect the land by the application of farmyard manure contamin- ated with the germs of finger-and-toe, the Norfolk four-course rotation, modified as indicated, can be depended upon on most soils to secure sound crops of turnips or swedes. Then, again, if it is found that any particular farm or field shows clover sickness in a pronounced form, it may be necessary, instead of having one-fourth of the tillage area under clover, to be satisfied with only one-eighth ; the area of clover so displaced being cultivated with beans, peas, or vetches, crops, namely, of the same natural order as clover, and therefore capable of enriching the land with nitrogen derived from the atmosphere through the action of the minute organisms associated with their roots. So _ far as combating clover sickness is concerned, % =e a ROTATION OF CROPS 205 the object would be attained by growing Italian rye-grass, or some other non-legu- minous fodder crop; but, of course, under this system the land would not be periodically enriched with nitrogen. The Norfolk four-course shift has not attained to its present position of import- ance without resting upon a solid foundation of advantages, cultural and otherwise, which may be summarized as follows: The two principal cereal crops, barley and wheat, are . sowed at different times of the year, which is convenient from the point of view of the economical utilization of labour; moreover, they differ in the character of their root- system, barley feeding chiefly on the surface layers of the soil, whereas wheat penetrates deeply into the subsoil. Then, again, it is found that wheat grows well after clover, utilizing very fully the nitrogen stored up in the root-residues, and finding congenial con- ditions of growth in the compact clover sod. The clover crop, also, being removed from the land not later than July, permits of the ground being ploughed sufficiently early to admit of wheat being sowed at the best time of year—early autumn. It may be men- _ tioned that, if the land is not sufficiently clean, it may be broken up directly the clover 206 _- AGRICULTURE crop: is removed, the dry weather. of, late summer being utilized to cultivate the ground, and:to bring the weeds: to the surface, most of! which: will; by such: treatment, be killed under the influence of sun and drought.. In due course’ the wheat. will be harvested in August, and. the stubble, being broken up in autumn. or early winter, will be exposed. to the ameliorating influence of frost, which is the: most effective: natural.agent in the pro- duction. of the fine tilth that is. so essential to the cultivation of the turnip crop. Turnips conveniently: precede. barley, which is a cereal.crop that.can: be.sowed comparatively late-in spring, so. that’ ample time: is. given for. the consumption. of.a. proportion of the turnip crop on the land by sheep. Moreover, the: manure left by the folding of sheep remains near the surface after the. land has been. ploughed. with.a 6-inch furrow ;. and such disposition. of the sheep droppings admirably. suits. the shallow-rooted: habit: of the. barley. crop.. Along. with the barley are usually sown. the seeds. of. clover. or grass, and. these not. only find. congenial conditions of.growth in the clean, well-manured ground, but the.resultant plants. also grow well during summer under the comparatively mild shade of. the barley. crop, in. other. words, barley fe ROTATION OF ‘CROPS 207 ia said to be a good “nurse”: «for seeds.” ‘Under the Norfolk four-course shift in its simple form one-fourth of the tillage area 1s under “seeds,” as it is called, or, in other _ words, a one-year’s ley, the produce being ~ usually made into hay, though it may be grazed by sheep or other stock. In many parts of the country—notably the north of England and in Scotland, where land takes more kindly to grass, and where stock- rearing is of greater importance—the Nor- | folk rotation is modified in such a way. that, in place of the land being under seeds for one year, it is left down for two. The.effect of this modification is that less manual and horse labour is required, and greater. facilities are given for stock-keeping. Whereas the first year’s ley is usually made into hay, the produce of the second year is almost invari- ably treated as pasture. .Under this rota- tion—which is specifically known as ‘the Northumberland ‘five-course shift—the ley is generally followed by oats.. If wheat ‘is grown at all upon a farm managed on ‘this rotation, it usually comes after the root erop. In certain parts of the country, notably districts in Scotland where high-farming ‘is 208 AGRICULTURE practised, one finds the East Lothian six- course rotation in common vogue. Assum- — ing the tillage land to be divided into six © sections, the East Lothian rotation will run as follows :— 1. Turnips or swedes, receiving farmyard manure and artificials. 2. Barley, wheat, or oats, unmanured. 3. Seeds made into hay, receiving arti- ficials, usually about 2 cwt. of nitrate of soda, with or without some super- phosphate. 4, Oats,not infrequently top-dressed with about 1 ewt. of nitrate of soda. 5. Potatoes, liberally treated with farm- - yard manure and artificials. 6. Wheat, unmanured. Under this system, two-sixths, that is one- third, of the farm is annually dressed with farmyard manure, a condition of things that usually entails the purchase of a certain amount of such fertilizing material, and this assumes convenient proximity to a town or colliery, whence dung can be pro- cured. Besides the third of the farm annually dressed with farmyard manure, probably another third is receiving artificial manure, so that no less than two-thirds of the whole ROTATION OF CROPS 209 \ iy tillage axea is being dressed with fertilizers _ of one kind or another, a condition of things _ that fairly merits the term “ high farming.” It is evident, of course, that this six-course rotation can at once be converted into a _ rotation of seven years, by leaving down the _ seeds for two years instead of one. - On very strong land, such as is met with in the Holderness district, a six-course rota- tion is practised which bears this name, and may be set out as follows :-— Turnips, swedes, cabbages, or mangolds. Wheat. Beans or clover. Wheat. Clover or beans, the beans being put on land previously under clover and the clover on land previously under beans. 6. Wheat. With the exception of the turnips these crops are all strong-land crops, and it will nibs wae eels He be seen that three-sixths, that is, one-half, _ of the farm is annually under wheat, while other two-sixths is under a _nitrogen-col- lecting, ¢.e. a leguminous, crop. On the strong carse land of central Scotland __ the following eight-course is not unusual :— 210 AGRICULTURE ‘Bare fallow. Wheat. Beans. Wheat. Turnips. Barley. Seeds hay. Oats. OUD oe Ob Here, as under the Norfolk four-course shift, 7 one-half of the farm is annually under a | cereal crop, and .one-fourth under a legu- 7 minous crop, assuming that the seeds hayis © principally red clover. On the other hand, | only one-eighth of the farm is under turnips, this crop being rather uncertain and difficult — | to grow on the strongest classes of land. On a strong-land farm where dairying is practised, and where, consequently, every effort must be made to secure a root crop, turnips or swedes are frequently grown after ~ bare fallow, a system that permits of the | production of the finest tilth that can be ~ secured. Dung having been spread in ‘the | drills in autumn, the land is ridged up and left lying fully exposed to the frosts of — winter, and in the month of May, after artificial manures have been sowed broadcast _ over the ground, the ridging plough is run ROTATION OF CROPS = 214 etween the. drills. to. collect all the fine mould: along the lines. where the turnip seed is.distributed, _ In the. east. of. England, notably Norfolk, : ‘Suffolk, and Cambridgeshire, where the highest - quality of barley is grown, the Norfolk four- ore shift. is modified'as follows :— 1. Roots. 2. Wheat. 3. Barley. 4, Seeds. 5. Oats, or wheat. Here. barley. follows’ wheat, as it’ is. found that in this way. malting barley of the highest quality: can. be’secured, although. at. the cost . of some reduction. in. quantity. If. barley - immediately follows roots, especially: if: folded by sheep, it frequently. obtains more nitrogen from the manurial. residues than. is. con- sistent. with the production of grain of the 4 | ene a class. What the maltster wants: in gap is a high. percentage of starch, with as little proteid) or nitrogenous substance as possible. ‘The introduction of wheat | between roots and-barley reduces the nitrogen _ contents of the soil; so that the barley that 212 « AGRICULTURE In parts of the country where the potato — crop is of special importance, a rotation is selected which will permit of a large pro- portion of the farm being put under this — crop. If the farmer is satisfied with one-fifth — of his total tillage area under potatoes, he can select the Norfolk four-course shift and | introduce potatoes between seeds and wheat, thereby converting a four-course into a five-course rotation. Potatoes are found to grow well after a one-year’s ley, but if one- — fifth of the farm is not considered sufficient for the potato crop, part or all of the “* break ” that would, under ordinary circumstances, be devoted to turnips or mangolds can also. be placed under potatoes. If all the root break were given over to potatoes, it would mean that a farm worked upon such a five- course rotation would show two-fifths of the whole under this crop. It is in districts where the climate, soil, — and system of farming encourage the cultiva- | tion of catch- “crops that the planning of a | rotation requires most attention. On the — extensive tracts of Down land in the south and east of England, where sheep-breeding is the mainstay of farming, the system of cropping is primarily arranged to provide a continuous supply of suitable green food ‘ROTATION OF CROPS 218 | for the sheep flocks during the greater part | of the year. During winter, turnips and ‘swedes are chiefly depended on, followed | by winter rye, winter barley, winter vetches, | kale, rape, and crimson clover, to be con- “sumed throughout March, April, and May. During the consumption of the crimson clover and rye, the sheep are often allowed @ certain quantity of mangolds, which are either cut and placed in troughs, or are thrown down whole in the daily fold. By the time these crops are consumed, ordinary } clover and seeds’ mixtures are ready for folding, or the flock is turned out to graze in the open field or upon the Down. . About the month of July the aftermath of the clover is ready to be folded, to be followed later by mustard and early turnips. Rape is a great stand-by in Down farming, it being consumed either in autumn or spring, when, often in conjunction with thousand- headed kale, it gives a large quantity of - succulent food. The yields of some of the crops mentioned are, in the districts indicated, too small to make it profitable for the farmer to devote a whole year to the growth of the crop con- cerned. He must therefore endeavour to ‘grow such a folding crop as mustard, crimson q ‘ | Ze ) SNRs | Mate 214: AGRICULTURE — clover,,or. winter rye, between two’ principal crops of: the farm, hence the origin of the © expression “catch crop.” In the north of England, and throughout Scotland, the © climate seldom, admits of. catch cropping, © though in some of. the better. districts: of © Scotland one finds farmers sowing Italian © rye-grass. after. an early crop of potatoes, — the grass being removed by the end of May © or beginning of June in the following year, ~ in time to permit of its being followed. by © a.crop of turnips. Sometimes-also a farmer © is able to harvest his. crop of red clover | before the. end. of. June, and. if: he is. very 4 expeditious. he may. succeed. in getting the. { ground ploughed and. sufficiently cultivated — to permit. of. the sowing. of a crop of whitell : turnips. In. the north,. turnip. seed is not 7 infrequently grown as a catch crop after / clover, early. potatoes, or Italian rye-grass. © The. seed: is ripe about the end, of May, 7 and, if sowed. before the beginning of: July, ~ sufficiently robust plants will) be produced to. withstand the winter. In the following year the plants shoot out to produce seed, which is harvested, as has already: been said, about. the end of May, to be followed a | Italian rye-grass; or some such crop. It. is, however, in the warmer: and: drier “ROTATION OF ‘CROPS 215 | ‘dis istricts of England that .catch cropping | f fi nds its greatest development. Not only i | aust the climate be good, but the soil must > fairly light, so that there is no difficulty a bs securing a good seed-bed in the minimum of time after a crop has been removed from the land. Strong land makes catch cropping ‘practically impossible, it being difficult to ‘plough such land during dry weather at the | height of summer. Even if it be broken up ' at great expenditure on horse labour, or reek the utilization of steam, the furrow 4s so rough and intractable.as to be incapable ot yielding a satisfactory seed-bed, without Pike intervention of a long period of exposure i sun and air. But it is of the essence of success in catch cropping that no time should be lost between the separation of one crop _ from the land and the sowing of the next, and _ this is only possible where the land is of such a. character as to permit of its being ploughed and otherwise worked under practically any _ conditions of weather. | By way of illustrating the practice of _ eatch cropping we may take the following rotation. Wheat having been harvested and ‘cleared from the land by the middle of | August, the stubble is immediately scarified, either by horse or steam power, so that 216 AGRICULTURE most of the weeds are dragged to the surface and destroyed. In this way an excellent seed-bed is prepared for the broadcast sowing of crimson clover or stubble turnips, the) former furnishing valuable folding food in_ the following spring, while the turnips can be utilized at any time during winter. Or the wheat stubble may be ploughed with a_ shallow furrow and sowed with white | mustard, which in six weeks will be ready © for folding, and is largely used in the south ~ of England for “ flushing’? the ewe flock © during the month of October. In the mildest — districts rape may be sowed instead of © mustard; and when the weather becomes. — genial, about the beginning of March, the ~ plants shoot out rapidly, to furnish a large © yield of useful sheep “ keep.’? Whatever ~ the crop selected to follow wheat, it must | be cleared from the land not later than the ) middle of June, and in many cases the ground is cleared considerably earlier. When — the catch crop has been utilized the land is | at once ploughed and suitably dressed with | artificial manure, perhaps even with farm- — yard manure; and mangolds, swedes, or _ yellow turnips are sowed. Mangolds are sowed in the south at much the same time of the year as in the north, namely early in ROTATION OF CROPS 217 May, but in the south swedes and common turnips are not put into the land for a month or six weeks after the time at which they are sowed in the north of England and through- put Scotland. This fact explains, to some ie extent, the greater ease with which catch eropping may be practised in the south as Jeomparea with the north, though the harder winters of the north are the main restricting Biease There is not much chance of getting fa catch crop in between the mangolds, }swedes, or turnips, and the barley or other cereal that follows; nor is there the oppor- | tunity of catch cropping immediately after Hbarley, because that crop is usually sowed | down with “ seeds.’’ In a season of drought, | however, when the “seeds ” fail, the barley }stubble may be broken up, as in the case j of the wheat stubble, and similar crops may | be made to follow. As regards the “‘ seeds,” |: a catch crop may or may not follow, accord- ‘ing to circumstances. If the clover stubble is broken up by the end of June it is possible } to cultivate at least one crop of mustard | before the time for sowing wheat, which is ' the crop that generally succeeds “‘seeds.’? In | place of treating the clover stubble in this | way, it may be ploughed and, as it is called, 1 ‘bastard fallowed’’—that is to say, left | a * fi 218 AGRICULTURE uncropped, with occasional harrowings. and! srubbings—during the warm, dry weather of late summer, when weeds will be killed by heat’ and drought; and the land mellowing) under the influence of the weather. When) in September, so that wheat is sowed'in goc A time in the end of that month or throughout October. i crops should be grown in order that they may subsequently be ploughed into the land” to increase the stock of humus. There is no” doubt that such treatment’ has considerable” effect upon the fertility of the land, but it is” probable that, on the whole, greater advan-_ tage accrues to the farmer through the consumption of the catch crop by stock.” Theoretically a leguminous crop should be follow the use of white mustard. el Oe eS ae ee 219 ‘CHAPTER X SEED To secure success in. tillage farming, no i ttle attention’ must be ‘given to considera- is of seed. If one is using home-grown upp, one may ‘have to be satisfied -with 1 that would not make a very attractive ¢ eckét sample, or which does not: show very ye high power of germination. Seed produced ‘on the farm is not valued at so high a rate as Se sed that is imported, so that one can -afford to sow-somewhat thicker, and thus make-up Yor impurities such as chaff, husks and ‘grit ; ‘but only under ‘rare circumstances would e be justified in using any -seed whose mipurities -were weeds. One of’ these “rare exceptions -would -oceur ‘where “poor ~ foul land was being seeded, for-with weeds natur- ally present in practically unlimited quantity, the addition of a few more ean make very little | difference Tf, however, one is purchasing ‘seed, one should take ‘purity, cleanness, and -@erminative capacity into serious account. As aah “purity, ‘it is evident’ that a pur- chaser wants tobe sure of obtaining the rtieular ‘species or variety of plant that by bd e | } | q 220 AGRICULTURE | he desires. In some cases it is not difficult to determine whether a sample or consign- ment of seed is true to name, but in other cases one must rely upon the character of the vendor for careful business methods and upright dealing, or one has to wait until the resulting plants have grown sufficiently to disclose their identity. It is, of course, a simple matter to distinguish the seed of barley from that of oats, or the seed of rye grass from that of Timothy; but it is not so easy to distinguish rape seed from swede seed; while it is practically impossible to detect any difference between the seed of - varieties of swedes, or between Broad Red Clover and Cow Grass. Mistakes on the part of sellers have occasionally led to expensive arbitration or litigation, as, for” instance, where two-cut sainfoin has been supplied for the single-cut variety, or where’ rape seed has been inadvertently supplied to a purchaser of swede seed. Purity is concerned not only with the question of differentiation between closely | related varieties, but also with freedom from the seeds of indifferent or positively injurious plants. Apart from the case where a sample contains the spores of a destructive fungus like Smut, one may meet, in a seed sample, | Oe eid SEED 221 vi th the seeds of such a pest as Dodder, ‘a parasitic plant of the natural order Con- 'volvulacee, which by attaching itself to ‘clover, flax, and certain other cultivated T fants, is capable of doing a large amount pot harm. Or the impurity may take the form of weed seed, such as Twitch, Bindweed, ‘Sorrel, and many others. Such an impurity ‘is objectionable on many grounds, not only ‘because the higher the percentage of impurity ‘the less the percentage of the seed that one i desires to purchase, but also because, through ‘the agency of such impurities, weeds may be introduced to land hitherto clean. The . — of impurities is of least importance i where the seed is to be used upon land that | is by no means clean, and becomes of the i highest importance where one is cultivating land as free from weeds as it is possible to , i secure. _ Cleanness, as apart from purity of species, Beans the absence of chaff, empty husks, grit, )sand, and the like ; and while such substances are not positively harmful, their presence in a 4 sample necessarily depresses the percentage -§ of the seed which one desires to sow. fe. In purchasing seed of all kinds, one should ; ‘e a a Tule a = that which is of high 222 AGRICULTURE that varies greatly in ‘the seed of different | species, some, like cereals, turnips, swedes, : and clover, usually germinating within a | fraction of 100 per cent., while others, such as the smaller grass: seeds, frequently fail: to - germinate over 80 per cent. ‘Other things) being equal, seed of high germinating power | is usually cheapest, because a ‘less quantity : is ‘required, and the resulting plants are’ usually stronger and more vigorous. A sample of seed of low germinative capacity : is usually in this condition either because: it is immature—that ‘is ‘to say, is insufficiently ; ripened—or because it is old—that is to say, not of ‘the immediately’ preceding crop— or because it ‘has “heated”? in the stack, or at some other stage of its history. One” will always find in the case of a poor sample, that many of the seeds that germinate: produce plants so feeble as to be unable to: survive the first few weeks, or it may be days, of ‘the conditions that they meet with on: an ordinary farm or garden. It is evident, therefore, that a laboratory test, conducted as it is under conditions specially favourable to germination, and stopping at the -point where sprouting occurs, supplies figures ' that unduly favour poor seed. | ‘The’ ‘* Real Value *? of a sample of seed is tee ‘ # i . SEED 223 got by regarding both the purity (including | cleanness) and germinative capacity, and _ is usually stated in the form of a percentage. | Suppose, for example, that a sample of cocks- | foot seed germinates 90 per cent. and has a | purity of 90 per cent., the Real Value—that is ' tosay, the number of seeds in 100 that are both | true to name and capable of germinating— isobtained by multiplying 90 by 90, and divid- | ing by 100, which gives’ $1. Or, to take | another case, if the purity is 90 and’ the a serminative capacity 70 per cent., the Real a Value works out at 63: Suppose that in the ta case of the sample having a Real’ Value of 81 4 the price is 1s. per lb., the value of the other a will be got by multiplying 12d: by 63 ' and dividing by 81, which gives a figure of .. © tactically 9id. This is really more than | the inferior sels is worth, for the reason | already given, namely, that where the 4 germinative capacity is low, many seeds § which would count in a test of germination | are of no practical value. Most farmers must annually purchase a of one kind or another. Speaking ‘i _ generally, farmers do not raise their own i. parase seed, turnip and swede seed, mangold seed, clover seed, and the like; therefore, i» for such seeds’ a farmer has usually no 224 AGRICULTURE alternative but to go into the market and purchase. In respect of this, however, custom differs in different parts of the country; for whereas it is rare to find English farmers growing ryegrass for seed, it is almost the rule in many parts of Wales, in the north of Ireland, and in the south-west of Scotland. Again, as regards turnip and swede seed, one finds in the north-east of Scotland that most farmers annually select a number of their best bulbs, and plant them out on some spare piece of ground, in order to supply themselves with home-grown seed. The growth of turnip seed requires some little care and the exercise of some intelligence, © for the bulbs have to be selected with dis- — crimination, and have to be grown at a distance from other cruciferous plants in flower, by whose pollen they might be con- ~ taminated. Then, at the season when the © seed is approaching maturity, the plants, © must be scrupulously protected against © sparrows, finches, and similar seed-eating © birds, which seem to be willing to run any © risk for a meal of turnip seed. The growthof » clover seed is even more restricted than that | of rye grass and turnips, the crop being culti- — vated for seed practically only in the warmest | and driest parts of England and Ireland. SEED 225 _ Apart from cases where farmers, not having home-grown seed, must go into the market and purchase, many circumstances may arise to make it desirable that a farmer _ shall import seed to his holding, even where } he has supplies of the same species, and even } of the same variety. From time to time _ seed-growers or importers place varieties on | the market which possess specially desirable | characters, such as productiveness, early | ripening, good standing power, ete., and it _ may pay a farmer to sell seed which he would | otherwise use, and to purchase a new strain of the same variety. | Then, again, it is found from experience } that seed from a different soil, or a different climate, produces plants of greater vigour | than is displayed by crops of the same variety | which has long been grown on the same | holding or in the same district. In the case | of certain plants and animals a change of soil } and climate seems to impart a vital impulse } that at once arrests attention. The cause f may be obscure, but the result seems to be | illustrated i in the wonderful productiveness of rabbits in Australia, 3 in the great size of trout in New Zealand, in the extraordinary vigour { of English thistles on the pampas of South America, in the aggressiveness of Canadian 226 AGRICULTURE pondweed in some British lakes, and in the way in which European weeds have monopolized the pollution of Canadian fields. It is found in the case of cereals that if seed be obtained for a backward farm from a much earlier district, the crop grown during the first year or two ripens earlier, and furnishes a brighter’? sample than the same variety which has all along grown in the particular district. Generally speaking, farmers import seed | from a dry climate to one that is moist, and not vice versa; and such practice appears to be based upon sound physiological grounds. A variety that has long grown in a district of low rainfall, and with relatively dry air, - has adapted itself to make the most out of such conditions. The cuticle, epidermis, and stomata of its leaves have developed in such a@ way as to retard expiration of water, with the result that it can flourish luxuriantly even when soil-moisture is not abundant, or where the conditions encourage excessive evaporation. These peculiarities are carried in the embryos when the seed is transferred — to a new district, and even if the quantity of moisture in the soil and air there be much greater, the resultant plants seem capable of rapid adjustment to the new conditions, Bie Nag IS Tere = SEED 227 and show successful growth. On the other hand, a variety that has grown for years in a wet climate exhibits modifications of the leaf tissue, and develops a different type of stoma, and if the variety, so modified, _ be moved to a dry district, it seems to be incapable of placing itself sufficiently quickly - in harmony with the new environment to show immediately vigorous growth, though this may come with years of adaptation. On the contrary, it continues to transpire large quantities of water, which, though ‘not excessive where supplies are abundant, must be so designated where supplies are restricted. Sometimes a farmer is forced to purchase seed, by reason of the fact that his home- grown supplies are much contaminated by impurities. On some farms, for instance, wild oats are so abundant that home-grown grain cannot be used as seed. The case of seed potatoes is not quite on all-fours with those just indicated, because the potato crop, as the term is ordinarily used, is not grown from seed but from cuttings; propagation, in the agricultural and horticultural sense, being directly com- parable with the raising of poplars, willows, gooseberries, and currants, from cuttings, H 2 228 AGRICULTURE or of apples and pears by grafting. Sucha | method of increase is called vegetative, as opposed to propagation by means of seed, which is defined as sexual reproduction. In the case of the potato, what appears to determine the health of the crop, and a large yield, is strong development of the corky layer which envelops the tuber, and of the epidermis and cuticle of the leaf and stem. If these protective coverings are thick, the plant is able to offer successful resistance, more or less complete, to the attack of the many parasites that prey upon it. In inclement districts there is a tendency on the part of all plants, including potatoes, — to develop a thick skin as a protection ~ against the severe conditions of the environ- ment; and when such thick-skinned tubers are subsequently planted in a district with a better climate, they still, for some years, retain their acquired characters, with con- sequent comparative immunity from disease. © It is possible, also, that tubers being less © fully matured in a late district, sprout more | vigorously when used as “seed.’’ But, whatever the reason, it is at all events the — practice for growers, in the best potato | districts, such as East Lothian, Lincolnshire, — Bedfordshire, and Cambridgeshire, to import | SEED 229 their seed potatoes from Scotland and Ireland ; Jersey, for instance, taking considerable quantities from the Isle of Skye. Perhaps there is no crop on the farm for which a farmer goes more frequently into the market for “seed” than potatoes. Not only is the yield found to be increased _ by obtaining fresh seed from a more incle- ment district, but new varieties are con- stantly being put on the market which are distinguished for some desirable property— prolificness, resistance to disease, etc.—and ' enterprising potato growers naturally desire to make trial of such new sorts. It is found that in the course of time, varieties, which in the early years of their existence were practically immune from disease, lose their constitutional vigour, and are no more resistant than those that they supplanted. When this stage has been reached, the neces- sity for a change of seed becomes pressing, so that from one consideration and another potato growers are constantly on the market for fresh seed. Twenty years or so ago the varieties that held the field were the “Champion,” ‘‘ Bruce,” ‘‘ Prince Regent,” ete.; and, more recently, ‘‘ Up-to-date,” ‘“‘ Farmer’s Glory,” ‘‘ Factor,”’ ‘“‘ Abundance,” and others, have enjoyed a high reputation, 230 AGRICULTURE no doubt, like their predecessors, ultimately to give way before newer varieties. New varieties of potatoes are all obtained by raising seedlings, which are either got by the indiscriminate sowing of the seed of the berries, or are the result of the definite crossing of distinct varieties. Most of the seedlings are no improvement on _ their parents ; but, by careful selection, a certain proportion showing desirable features may be separated out, and when these have been vegetatively propagated in sufficient quantity they are distributed ee the ordinary trade channels. Not only have certain error te of potato exceptional powers of disease resistance, but the same is also true of other plants, such’ as wheat; Rivet or Cone, for instance, being much more resistant to rust than others, such as Michigan Bronze. From time to time, also, varieties of turnip with marked powers of resistance to the attack of finger- and-toe are put on the market ; and similarly in the case of gooseberries (resistance to American Mildew), apples (resistance to canker), ete. Many individuals and commercial firms are engaged in this and other countries in attempting to improve existing varieties of Sai 3! SO es es eee — - a goss " ’ ; 5 ee Re : a . ‘Sp Sern 3, hee SS ee phe ode ts bo eS ee eed A i aa t ee ee ee ee —— a Nt eee GE ae. =e 2 Pe P a 2) ‘ i PONT Ferme eri i 3a lit prrns z TEST riers oats =e sibh Aad ha enh inal pokes Edam anakda eealinenialinde ean et nae eet ae FA) PETE he ry eTe eye = 7 gr Po Cl a - “ Se CSN ee Rees 2 ee) SEED 231 crops through the agency of seed, that is, by breeding. While many of the varieties so produced are hardly an improvement upon their predecessors, there is no doubt that many notable successes have been scored, and on the whole the character of our farm crops, and, it may be added, of our farm - animals, has undergone great improvement _ during the past fifty years. The improve- - ment of plants by breeding takes two lines, improvement by selection, and improvement by crossing or hybridization, and as a rule - both of these lines are followed in arriving | at the final product. In attempting to improve plants by selection, one takes such opportunities as present themselves of col- lecting the seed of those individual plants which show in a marked degree the qualities that one desires to see in the progeny. By collecting seed from a number of individuals one does not obtain a pure strain, although the crop in bulk may have desirable char- acteristics. To obtain a pure foundation : - gtoeck one must start with the seed of a | single plant, sometimes even with a single grain, and although this method. of pro- cedure is slower to furnish results, it is probably more satisfactory in the end. Of course, even where one selects seed from a 232 AGRICULTURE large number of individual plants, one can obtain a pure foundation stock from the best single plant that results from sowing the mixed seed. What the chuchchers shall be that the plant breeder fixes his attention on, must depend on circumstances. Even within the limits of a single plant-species, such as wheat, one has many characteristics to choose from, such as yield, freedom from rust, strength © | and length of straw, presence or absence of awns, colour and hardness of grain, colour _ of husk, time of maturing, tillering, resistance to weather, and others. In breeding turnips, kohl-rabi, swedes, and mangolds, the object that one principally desires to secure, besides ~ a large yield and good keeping properties, — is a high percentage of sugar, because it is ~ chiefly this substance in the crops indicated _ that determines their feeding properties. On the other hand, what one wants to secure in potatoes, besides yield and freedom from disease, is a high percentage of starch, for on this constituent depends the desirable || culinary property of mealiness. On the _ Continent, where enormous quantities of potatoes are distilled for the production of — spirit, a high percentage of starch is even - more important than in this country. In | SEED 233 the case of barley it is starch also that is all- important, because it is this substance which, when treated on the malting floor, changes into maltose; and this, when fermented, | determines the quantity and quality of the product of breweries and distilleries. Having secured a foundation stock of _ Individual plants which show the desired characters, one proceeds to cultivate them ' year after year, being careful to eliminate and destroy any individuals which show undesirable variations, or which tend to | ‘ hark back to the original strain. On the other hand, one retains the seed of such plants as display the characters that are considered desirable, and so, in the course of time, by the process of elimination and selection, one obtains a large supply of seed of some new and improved variety of crop. In the case of wheat, barley, and oats, which are self-fertilizing, one will find practically no tendency to vary, if one sows only the seed of a single individual plant, and if no artificial cross-fertilization has been performed. Selec- tion, therefore, is of importance, in the case of these plants, only in securing the parent type. | Improvement by selection depends prim- arily upon a property in plants and animals 284 AGRICULTURE called variation, which means that although the progeny resemble the parents, the re- semblance is never quite complete. Without variation there can be no improvement, Variation may mean much or little, it may imply some small divergence from the original type, which is so inconspicuous as to be impossible or difficult of detection; or it may mean a sharp departure from the original type, in which case it may merit the term “ mutation” or “sport.” Sports may instantly give rise to a new breed, whereas, in the method of improvement by selection throughout a series of generations the breed is secured slowly and with more difficulty. Animals more than plants fre- quently show a tendency to reversion or atavism, which means that the organism is reproducing certain characters possessed by an ancestor, but not by an immediate parent. The ancestor may be no further back than two or three generations, or it may be much more remote. In the practice of breeding, no matter which line is adopted, one must see that the individual plants one propagates from year to year are given precisely similar conditions of growth, because it is only by attending © to this matter that one can be sure that SEED 235 robustness, or the opposite, in individuals is due to inherent qualities, and not to the influence of the environment, in the widest sense of the term. It was chiefly by methods of selection that the old breeders, such as Le Couteur, Chevalier, Hallet, Lawson, Shirreff, and others, secured ee the results that have made their names _ famous. At the present time simple selection is | still followed with good results, but better and more rapid results often attend selection that has been preceded by crossing. For example, one may take two individual plants of a species, such as wheat or oats, that usually shows self-fertilization, and, with the adoption of precautionary measures that need not be gone into here, one transfers the pollen of one plant to the stigma of the other, and, if fertilization has succeeded, one obtains a eross which combines in it, latent or con- spicuous, the characters of its parents. It is found that plants raised from seed that has been thus secured are much more liable _to vary than is the case with plants resulting from. self-fertilization. When one has, by this means, fostered the tendency to vary, one is given the opportunity of a much wider range of selection than would otherwise have been possible, and thus improvement begun 236 AGRICULTURE by crossing is completed by selection. It is found that even the crossing at random of different types often gives fairly good results, though greater success is secured by the union of types which display in a marked degree the characteristics that one desires. The best results of all, however, are obtained by careful selection continued throughout some years, until one has obtained a pure stock, followed by the mating of distinct individuals, the completion of the improve- ment and the fixing of the type being subsequently effected by the process of selection and elimination. By starting in this way it is found that there is much less tendency to reversion to undesirable char- acters. When one mates two individuals possessing special characters, these characters may be so intimately blended in the progeny that it is impossible to say that the peculiarities of one parent are more conspicuous than those of the other. On the other hand, it very frequently happens that the offspring shows the characters of one parent only, those of the other being latent, although they are capable of displaying themselves in sub- sequent generations. The term applied to this condition of things is prepotency, which Ns ayigea te eee BS Sega eee SEED 2387 | may be conspicuous without being exclusive, but may also be so assertive as to be absolute. Then, again, when the characters of the parents are reproduced in the offspring they may be equally intermingled, or they may appear in patches. In cattle the former condition of things, so far as hair colour is ’ concerned, is illustrated in blue-grey Short- horn-Angus or Shorthorn-Galloway calves, where the whiteness of the father and the blackness of the mother reappear as black and white hairs which occur equally all over - the animal’s body. The other condition of things—inheritance of colour in patches—is illustrated by the piebald, where the black and white colours are separated in distinct areas. This result is called particulate in- heritance, and amongst plants is best illus- trated by that curious hybrid laburnum, Cytisus Adami, which is a cross between the ordinary laburnum with yellow flowers, and another laburnum whose flowers are purple. In Cytisus Adami we find flowers in whose petals the colours of both parents are blended ; but we have also, on the same plant, yellow flowers, which are indistinguishable from those of the common laburnum, and purple flowers, of precisely the same colour as those of the purple parent. 238 AGRICULTURE During the last ten years much of the work of plant breeding has followed what are called Mendelian lines. The name is derived from an Austrian monk who, about the middle of last century, occupied his leisure with plant breeding, and although his results appeared in a local publication, it is only of late years that they have attracted much attention. Hitherto plant and animal im- provement by crossing has been slow to furnish stable strains, for the reason that one has never been sure how to select from the progeny those individuals that were of a fixed type, and would therefore breed true. Mendel, however, showed that the characters of the parents are transmitted to the offspring according to a definite law, now known as Mendel’s law, by the observance of which very striking results have been secured in a remarkably short space of time. The law, no doubt, appears to break down at many points, but this is probably due in most, if not in all, cases to the fact that the parents are not ‘‘ pure-bred,” in the strict sense of the term. Mendel’s experiments were carried out with peas, some plants of which he found to possess the character of tallness as con- _ trasted- with dwariness, greenness in the seed as compared with yellowness, wrinkled seed Oe ISHED (7°: 239 in place of smooth seed, and purple flowers | in place of white. For the purposes of illustrating his law we may take the char- acters of tallness and dwarfness. Mendel | found, when he mated a tall pea with a dwarf pea, that the seed so produced grew plants which were all tall, and, so far as external appearances went, it was impossible to tell any difference between the various individuals. When he allowed these tall peas to fertilize themselves, he secured. seeds which produced plants, some of which were . tall and some of which were dwarf. As a matter of fact, by breeding many hundreds of individuals, he found that the tall peas as compared with the dwarf were nearly in the proportion of 8 to 1. When the dwarf peas of this generation were allowed to fertilize themselves, it was found that they all bred true, showing no disposition what- ever to revert to the tall type, and this purity of breeding was found to continue through successive generations. As regards the tall peas of the second generation, how- ever, Mendel found that whereas a certain number of them could be depended on to _ give seed that would only produce tall individuals, the larger number of the tall peas of the second generation yielded seed that 240 AGRICULTURE produced plants partly tail and partly dwarf. As in the second generation so in this—the third—these dwarf individuals could be depended on to breed true to type, a condition of things that was continued throughout an indefinite number of subsequent generations. But the tall peas of the third generation did not all transmit their character throughout the following generations, only some possess- ing this power. The results can be best set forth in such a diagram as is here inserted. Tall Dwart | | Tall * Tall ° Tall° Dwarf * | | | Tall * Tall ° Tall° Dwarf * *— Will breed true. . °= Will not breed true. This work of Mendel’s has been fully ~ confirmed by other investigators, so that it © may be confidently predicted that tall and | dwarf peas, if bred together in sufficient — numbers, will produce similar results in the _ generations that follow. ; Of late years Mendel’s law has been applied __ = _— — SEED 241 | with great success to the breeding of wheat, and as an example of the applications of his _ law we may take the crossing of two wheats, _ the one possessing a lax ear, and the other an ear that is dense. When such wheats are interbred they produce an offspring whose ear stands intermediate between the cha- racters of the two parents, that is to say, it illustrates the law of blended inheritance. When the individuals of this first generation, showing intermediate characters, are allowed to exercise self-fertilization, it is found that .in the next generation 25 per cent. of the plants possess lax ears and will breed true, that other 25 per cent. possess dense ears and will also breed true, whereas 50 per cent. of the plants possess ears that are inter- mediate between laxness and denseness, and these when self-fertilized do not breed true, but produce offspring showing the same percentages of laxness, denseness, and inter- mediacy as was displayed in the second generation. We can take the simpler case of pea breed- ing from tall and dwarf parents to give a general illustration of the law. The character —in this case, dwarfness—that comes out in the second generation in individuals that breed true, and which was masked or obscured 242 AGRICULTURE in the first generation, is called a “‘ recessive ” character ; whereas the character which was exclusively present in the first generation, and which was also displayed by 75 per cent. of the individuals in the second generation, is called the “dominant” character. The general law may be expressed by means of such a diagram as is here inserted, where D stands for a dominant character, and R for a recessive. Plants possessing the recessive character, if self-fertilized, all breed true, whereas of the plants in the second generation that possess the dominant character only one-third breed true, two-thirds breaking up in the proportion of three dominants to one recessive. D R | | | D (impure) | | : | | D (pure) D (impure) OD (impure) R (pure) | p (pure) b (impure) " (impure) H (pure) It may be asked: If in the second generation we get pure recessives and a certain proportion of pure dominants, what is the advantage of crossing as compared with sticking to the me i a ali ee OR ne Lt ee ne SEED | 248 original parents? There are many advan- | tages, but one obvious one is that the parent _ possessing a dominant character may also | possess another desirable character that the recessive parent has not got, and it is thus possible ultimately to raise a strain possessing P= pot only the recessive character, but also the desirable character of the original dominant parent. _It has not been possible to classify all plant characters into the two groups of ‘‘ dominant ”’ and “recessive,’’ but sufficient work has _been done to enable us to state with con- fidence that the following characters are dominant: in the case of peas, tallness, round and green seed coat, yellow colour of the material (cotyledons) within the seed coat, and purple colour in the flowers; whereas the opposite characters, namely, dwarfness, wrinkled seeds, white or yellow seed coat, green cotyledons, and white flowers are recessive. In the case of wheat the absence of awns (beardless), lateness of ripening, and sensitiveness to rust are dominant; while the presence of awns (bearded), early ripening, and immunity from rust are recessive characters. Having indicated circumstances under which it is desirable and may be necessary to change seed, a few words may be added with 244 AGRICULTURE regard to other considerations that should be weighed before committing the seed to — the land. In some parts of the country one finds that a particular variety of crop is invariably sowed broadcast, while in another district the common practice may be to sow it in rows or, as it is commonly called, to drill it. The advantages and disadvantages of these two methods of seed distribution, and the special circumstances to which each is applicable, may be shortly discussed. When seed is distributed by a properly constructed drill that is adjusted satisfactorily, the grains are not only all covered with soil | but all are covered to a proper depth. In broadcasting, on the other hand, a certain. amount of seed will fall between clods or between the furrows and be buried too deep, while a certain amount will probably remain on the surface of the ground, and not be buried at all. The latter, if it escapes the attention of birds, may not germinate, or if it does produce plants these may be destroyed | by drought before they have secured a proper root-hold. With regard to the seed that is _ buried too deep, it may be deprived of the air that is an essential condition to germina- _ tion, or it may be in such a cold stratum of | soil that germination is retarded; and when ia SEED 245 it does produce plants these may have a difficulty in reaching the surface of the | ground, owing to the mechanical resistance of the soil, or because the reserves of plant food stored up in the seed are insufficient to maintain the plant until it has reached the surface, and unfolded its leaves to the ' influence of air and sun, and has begun to assimilate fresh supplies of food. The actual } depth at which seed should be deposited varies with soil, and with the character of the seed itself. Light soil, being better aerated and less resistant to the upward progress of the young seedling, can be placed over seed to a greater depth than clay soil. As regards the relationship of seed to soil covering, it may be said that, in general, _ the smaller the seed the shallower should be the covering, and the larger the seed the greater the amount of soil that may be spread over it. Beans, for instance, will easily reach the surface of the ground through three or four inches of soil, wheat may be _ buried to a depth of two inches, turnip seed is best covered with about one inch of soil, whereas many of the smaller grass and clover seeds can scarcely produce plants if they are buried under more than about half an inch of soil. 246 AGRICULTURE When seed is drilled all the resulting — plants have an equal amount of growing — space. It is true that in the direction of — the row the plants are much crowded, but — all have equal opportunities of spreading — their roots into the space between the adjoin- ing drills. On the other hand, where seed — is broadcast it can never be distributed with © such equality as to secure equal growing space to all the plants. In this respect, © however, a good deal depends upon the skill © of the sower, if hand distribution is practised, © or upon the efficiency of the machine, if © broadcasting is done by horse labour, but ~ more depends, as a rule, upon the character ~ of the surface of the ground. If the land has-_ been well ploughed, the conditions will be © most favourable to equal distribution; on — the other hand, with irregular furrows, the seeding may be very patchy. One great — advantage of drilling crops as contrasted © with broadcasting is that the former admits — of hand and horse hoeing, while the latter | does not, or only imperfectly ; and on land | that is much affected by perennial weeds, like twitch, or annual weeds, like charlock, | drilling is of special importance. It is also — found that less seed is required when it is _ drilled, chiefly because one can be more SEED Arr certain that all the seeds are distributed at Pach a depth as to secure the best conditions of germination and growth. Whereas 3-4 bushels of wheat per acre are necessary _where the seed is broadcast, it seldom | happens that more than 2-2} bushels are used | under a system of drilling. It is found that - cereal crops which have been drilled are less liable, as the harvest approaches, to be laid _by heavy rain or strong wind, than is the case with broadcast crops. This is probably _ due to the fact that where the plants stand in regular rows the sun is better able to get at the lower parts of the stems, and, as sunlight encourages lignification, such straw is stronger and therefore less liable to be _ beaten down by rain or wind. This considera- _ tion has greatest importance in the case of a variety of cereal which produces a large bulk of straw, or which produces straw that is known to be feeble. It is also evident that the matter is of special importance in the case of rich land, where “lodging ’”’ is most liable to occur. While birds may pick up a certain pro- portion of broadcast seed which is left exposed on the surface of the ground, it is probable that, on the whole, birds, and especially rooks, do greater damage to drilled 248 AGRICULTURE crops than to those that are broadcast. In | the latter case they have, as it were, to search for every individual grain, whereas, when the grains are sowed in definite rows, birds seem to learn the art of running their © beaks up the rows, and thus of securing rapidly a large percentage of grain. It © may be added, in considering the advantages ~ and disadvantages of the two systems, that © drilling crops is the more costly operation, — for whereas in broadcasting it is possible to do good work by hand or, with a simple and cheap machine, drilling entails the use of a somewhat expensive machine, and one which requires more horse and manual ~ labour, and covers a much smaller area in | the day. Before proceeding to sow, one ought also to consider the question of density of stocking. It is not the individual plant that we want to favour but the whole community, and, according to circumstances, this end will be secured by having due regard to the amount of seed that should be employed. Other things being equal, we would sow less seed on good soil than on poor, for the _ reason that in the former case we may expect each plant to grow more vigorously and to | reach a larger size. It is also found that — a SEED 249 1 ibillering that is, the production of several | i ms by one plant—is most associated with | fertile soil. Then, again, the variety is not | without influence upon the quantity of seed _ Yequired. Some varieties of cereal tiller | more than others, and consequently less ' seed may be used in their case. Speaking } generally, it is found that while many of _ the new varieties of oats give a large yield, | they show no great disposition to tiller, and, therefore, must be sowed 20-50 per cent. more thickly. Again, one would sow more _ thickly in a poor than in a good climate, because in the former the individual plants are less vigorous, and there is a greater _ percentage of loss amongst the seedlings in their earlier stages of growth. One finds, for instance, that in the more backward districts of Scotland oats are generally sowed at the rate of 6-8 bushels an acre, whereas in the best parts of that country, and throughout England generally, 3-4 bushels is considered a full seeding. Needless to say that the size and quality of the seed should be taken into account. In the case of oats, for instance, many of the newer varieties are distinguished by very large grain, and consequently there is a smaller number of grains in a bushel, than is the 250 AGRICULTURE case with certain other varieties. This, to : some extent, accounts for the necessity of sowing some of these new oats very thickly. — Seed that is well ripened and of high ger- — minative capacity may, of course, be sowed more thinly than seed of poorer quality. In the case of cereals, the great danger of sowing too thickly is laying or lodging, for the reason already given in discussing — the subject of drilling, namely, that the — greater the number of plants on a given area, the more completely are the sun’s rays excluded from reaching the lower part of the straw, with corresponding reduction in : lignification, and therefore with reduced — power to stand erect. But within reasonable’ limits thick seeding has its advantages. In diminishing lignification it results in the production of straw that is of superior feeding value; and it is possibly to some extent owing to the large quantity of seed © that Aberdeenshire farmers use per acre that the oat-straw of that country has such ~ high feeding value. Then, again, if straw | is to be used for textile purposes, such as making hats, horse collars, and the like, it is not desirable to have it much lignified, because it is more brittle and therefore less easy to manipulate. Where, therefore, straw a eet ee - > my OP Se AE ee Pe ee eee Sno ore oes SEED 251 is grown expressly for weaving, the seeding ‘is relatively dense. The most important textile fibre grown in the British Isles is : flax, and if it is the intention to work up | the product into linen, a larger quantity of |} seed is used than if the object is the pro- duction of linseed. | The density of the stocking, if not the | quantity of seed, has great influence upon the quality of such roots as swedes, mangolds, and sugar beet. These roots are all valuable for the sugar that they contain, and it is found that the percentage of sugar is lower ‘in large roots than in small ones. In the ‘ase of swedes and mangolds a superior quality of root may not compensate for Much reduction in the yield; but in the case of sugar beet it is the custom to cultivate the crop in such a way that. small-sized roots are produced, and these are not only re- latively richer in sugar, but, collectively, give a larger output of sugar per acre. i ‘ BIBLIOGRAPHY SOILS Hatt.—The Sotl (London, John Murray). The whole subject is handled in a masterly way. Whether as a text-book or a laboratory guide, it should be in the hands of every agricultural student. : HALL AND RussELL.—Agriculture and Soils of Kent, Surrey, and Sussex (published by the Board of ‘ Agriculture), An agricultural soil-survey of the South-East of England, where the relationship of — different types of farming to the geological con-— ditions is dealt with in an interesting and practical manner. | Kine.—The Soil (London, Macmillan & Co.). An- : American work smaller than the first, dealing more particularly with the physical aspects ‘of the subject. ( MacponaLD.—Dry Farming (Werner Laurie). A book by a man who has carefully studied the conservation — of water for agricultural purposes in districts of low rainfall in North America and South Africa. E Marr.—Agricultural Geology (Methuen & Co.). An } excellent text-book of geology in its bearings on ig agriculture. Traces the relationship of soils to geological strata, and contains much useful informa- . tion in regard to geological maps, __ Warineton.—Physical Properties of Soil (The Clarendon Press). A series of lectures delivered in Oxford, in which the subject is handled with the author’ 8. i well-known thoroughness. MANURING, CROPS, SEEDS, AND GENERAL Apiz anD Woop.—Agricultural Chemistry (Kegan Paul, ‘ Trench, Triibner & Co.). Two small volumes, con- taining, like some of the books below, information 252 | 5 a BIBLIOGRAPHY 258 Le | 4 about feeding stuffs as well as manures. The subject _ ig treated from the experimental standpoint: an ia excellent manual for students. _ Arkman.—Manures and the Principles of M anuring ise (Blackwood & Sons). A fairly exhaustive treatise 4 of solid merit. _ Dyrr.—Fertilisers and Feeding Stuffs (Crosby Lockwood). ad Quite a small book, but contains much information directly useful to farmers. It reproduces, with comments, the Fertilisers and Feeding Stuffs Act. - Dymonn. —Chemistry for Agricultural Students (Edward Pe - Arnold), A small book that can be thoroughly recom- ‘ mended as a guide to elementary laboratory practice. _ Fream anp Arnswortu-Davis.—The Elements of Agri- culture (John Murray). The best small general work | on the whole range of Agriculture. ~Hatt.—The Feeding of Crops and Stock (John Murray). ig An excellent treatise on plant and animal nutrition from the agricultural point of view. ~Bawtyi,—Fertilisers and Manures (John Murray). A thoroughly up-to-date manual by a sound authority, who knows how to make a technical subject in- 3 teresting. - Hatz.—The Book of the Rothamsted Experiments (John Murray). Indispensable to all who would inform themselves of the main results of this famous station. Prrcrvan.—Agriculiural Botany (Duckworth & Co.). A reliable and fairly exhaustive text-book. Pottrer.—Agricultural Botany (Methuen & Co.). A smaller work, but also excellent. | Ponnetr.—Mendelism (Macmillan & Co.). The best small 5 work on this subject. | Dr Vrius.—Plant Breeding (Kegan Paul, Trench, Triib- ner & Co.). Discusses standard methods of pro- | cedure, and goes in detail into the author’s own methods, as well as those of other experimenters, especially Nilsson & Burbank. Wazineton.—The Chemistry of the Farm (Vinton & Co.). An excellent small text-book on the subject, but _ by no means elementary, ; INDEX Amelioration of land, 73. Ammonia and nitrogen, Rela- tion between, 121. Artificial manures, Use of, 161. Atavism, 234. Attraction of soil, Surface, 29. Bare fallowing, 96. Barley in rotation, 211. Basic Slag and Superphos- phate, Relative values of, 126. Basic Slag, Valuation of, 138. Blood Meal, 125, 147. Bone Ash, 137. Bone-manures, 144. Breeding plants, 232. Broadcasting seed, 244. Caleareous soil, Properties of, 58. Calcium cyanamide, 124. Capillarity in soil, 28, 30. Carbonic acid as‘a weathering ¥* agent, 20. Catch-cropping, 212. Chalk soil, Properties of, 58. Changing seed, 223. Citric-soluble phosphate, 141. Clay burning, 87. Clay soil, Properties of, 55. Cleanness of seed, 221. Clover sickness, 133, 193, 200. Cohesiveness of soil, 24. Denitrification, 65. Density of seeding, 248. Disease-resisting plants, 230. Dominant characters, 242. Drainage, Effects of, 76. Drainage of land, 74. Dried blood, 125, 147. Drilling seed, 244. 254 Ce ee See ee ~~ os sf Dry farming, 31. Dung, Output of, 177. East Lothian rotation, 208. Essential elements of plant food, 106. Experiments, Field, 168. Fallowing, Bare, 96. Farming, Dry, 31. Farmyard manure, 173. Field trials, 168. ‘ Finger-and-toe, 93, 167, 193, 200. f Fish guano, 147. Formation of soil, 9. Four-course shift, 203. Frost uprooting plants, 77. Frost a weathering agent, 17. Gas lime, 94. et Glaciers as soil-forming agents, 23. ; Grass land, Effects of phos- phates on, 132. Green manuring, 51. Ground lime, 92. Guano, Fish, 147. Guano, Ichaboe, 160. Guano, Peruvian, 160. Guano, Phosphatic, 147. Heat, Absorption of, 41. Heat of oxidation, 43. Heat of soil, 38. Heat, Sources of, 42. Holderness rotation, 209. Humus, Properties of, 60. Hydration as a weathering agent, 14. Ichaboe guano, 160. Improvement of land, 73. | ensive agriculture, 53. vation, 83. ® init, 148. tand, Amelioration of, 73. he ; nd drainage, 74. ‘Law of Minimum, 106. I eguminose, Effects of phos- _ phates on, 131. ea plants and nitro- gen, 67. Lime, Nitrate of, 124. me removed from soil, 59. ..., Slaking of, 15. Limestone, 94. Liming, 91. ee Properties of, 57. “ Lodging ” of cereals, 250. I Mangels and nitrate of soda, 154. | Mangels and potash, 154. Manure, Farmyard, 173. | Manures, Nitrogenous, 110. | Manures, Phosphatic, 125. ) Manurial elements, 107. | Manuring, Green, 51. | Manuring, Principles of, 99. | Market gardening, 53. | Marling, 89. } Meat meal, 147. ; | Mendelian breeding, 238. fel s Law, 239. Mineral plant food, 34. ‘Muriate of potash, 151. Mutation, 234. | Nitrate of lime, 124. itrate of soda and sulphate of ammonia compared, 111. | n° of soda, Valuation of, i 8 _ Nitrates, Wovedion of, 61. ‘Nitrification, 61, 98. | Faittocen and ammonia, 121. Nitrogen, Fixation of, by soil,45. | | INDEX 255 Nitrogen in atmosphere, Com- bined, 70. Nitrogen- fixation by plants, 67. Nitrogen-fixing free organisms, 71. Nitrogenous manures, 110. Nitrolim, 124. Nodules on roots, 67. Norfolk four-course shift, 203. Organisms in soil, 71. Oxidation, a source of heat, 43. Oxygen as a weathering agent, 18. Particulate inheritance, 237. Peruvian guano, 160. Phosphate, Reverted, 167. Phosphates and phosphoric acid, 138. Phosphatic guano, 147. Phosphatic manures, 125. Phosphoric acid, Absorption of, by soil, 45. Phosphoric acid and phos- phates, 138. Plant breeders, Early, 235. Plant-breeding, 232. Plant food, Absorption of, by soil, 44. Plant food, Essential elements of, 106. Plant food, Fixation of, by soil, 44. Plant food, Mineral, 34. Plant food in soil, 102. Plants effected by climate, 225. Potash, Absorption of, bysoil,45. Potash manures, 147. — Potash and sulphate of potash, 148. Potash and potassium, 151. Potato disease, 228. Potatoes in rotation, 212. .- Potatoes, Raising new, 230. 256 » Potatoes, Seed, 227. Precipitated phosphate, 137. Prepotency, 236. Properties of soil, 24. Purity of seed, 220. Rape meal, 125. ** Real Value ”’ of seed, 222. Recessive characters, 242. Reversion, 234. Reverted phosphate, 167. Roots as weathering agents, 22. Rotations, 188. Rotations, Types of, 200. Sandy soil, Properties of, 48. Seed, 219. Seed, Change of, 223. Seed potatoes, 227. Seeding, Density of, 248. Selection of plants, 236. Sickness of clover, 133, 193, 200. Slag, Valuation of basic, 138. Soil, capacity to hold water, 27. Soil, Capillary power of, 28. Soil, Properties of calcareous, 58. Soil, Properties of clay, 55. Soil, Cohesiveness of, 24. Soil-cover of seed, 245. Soil, Formation of, 9. Soil, Properties of humus, 60. Soil, Properties of, 24. Soil, Properties of sandy, 48. Soil, Types of, 47. Specific heat, 39. ** Sports,”’ 234. Stassfurt mines, 147. Sulphate of ammonia and nitrate of soda compared, 111. Sulphate of ammonia removes lime, 59, 116. Sulphate of ammonia, Valua- tion of, 119. — Sulphate ‘of potash, 149. INDEX ss aRRaaneR Valuation of, Suparphosphat and basic slag, Surface attraction of soil, 29. © Three-field rotations, 202. | Turnip seed, Raising, 214, 224. Types of soil, 47. | Unit valuations, 120, 145, 149. Valuation of basic slag, 139. Valuation of bone manures, 145. Valuation of farmyard manure, | 175, 180. Valuation of nitrate of soda, 118, 120. Valuation of phosphatic man- ures, 137. Valuation of potash manureayy 149. Valuation of seed, 223. Valuation of ammonia, 119. q Valuation of superphosphate, 4 142. 1 Variation of plants, 234. Variations of temperature as a” weathering agent, 13. Warping, 90. 4d Water as a carrier of plant food, 34. d Water condensed from atmo- sphere, 37. | a Water depresses temperatur De 39, 76. a Water-holding power of soil, 27. Water asa weathering agent, 14 3 Weathering agents, 13. Wheat breeding, 241. Wheat rust, 230. i White clover, Effects of phos phates on, 129. Worms, Action of, 71. or PWC Rey aR IS Pees ome Home University of Modern Library Knowledge V. A Comprehensive Series of New 816. " {and Specially Written ‘Books 2/6 . net net. EDITORS : Pror, GILBERT MURRAY, D.Litt., LL.D., F.B.A. Mr HERBERT FISHER, M.A., F.B.A. Pror. J. ARTHUR THOMSON, M.A. Pror. WM. T. BREWSTER, M.A. ‘*The highly ingenious, attractive, and suggestive series of shilling books which now makes its bow to the public under the Home University Library’s ensign is the symbol, in somerespects of a revival, in others of a new era, in bibliology. In either case it is a symptom both of health and of hope in the future. ... 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