An operation which is, in some respects, the converse of warping, has been carried out on Blair-Drummond Moss, where the peat has been dislodged and carried off by the action of water, leaving the subjacent soil in a state fitted for cropping. Of course both this and warping are restricted to special localities, but they are most important means of ameliorating the soil when circumstances admit of their being carried out.

Mixing of Soils.—When soils possess conspicuous defects in their physical, and even in their chemical properties, great advantages may, in some instances, be derived from their proper admixture. A light sandy soil, for instance, is greatly improved by the addition of clay, and vice versa; so that, when two soils of opposite properties occur near to one another, both may be improved by mixture. It has been applied to the improvement of heavy clay soil and of peat, the former being mixed with sand or marl so as to diminish its tenacity; the latter with clay or gravel to add to its inorganic matters, and in both instances it has proved successful.

The process of chalking, which has been carried out on a large scale in some parts of England, and which consists in bringing up the chalk from pits, penetrating through the overlying tenacious clay, and mixing it with the soil, operates, to some extent, in a similar manner, though no doubt the lime also exercises a strictly chemical action. It is probable that the mixing of soils might be advantageously extended, and it merits more minute study than it has yet obtained. Its use is obviously limited by the expense, because, of course, where good effects are to be obtained, it is necessary to remove large quantities of soil, in some instances as much as 50 or 100 tons per acre, but the expense might be much diminished if it were carried out methodically, and on a considerable scale. The admixture of highly fertile soils with others of inferior quality is also worthy of attention; indeed, it is understood that this has been done, to some extent, with the rich trap soils of some parts of Scotland, but the extent of the benefit derived from it has not been made public.

FOOTNOTES:

[Footnote J: Mr. Dudgeon, Spylaw. Transactions of the Highland Society, vol. cxxix., p. 505.]



CHAPTER VII.

THE GENERAL PRINCIPLES OF MANURING.

In their natural condition all soils not absolutely barren are capable of supporting a certain amount of vegetation, and they continue to do so for an unlimited period, because the whole of the substances extracted from them are again restored, either directly by the decay of the plants, or indirectly by the droppings of the wild animals which have browzed upon them. Under these circumstances, a soil yields what may be called its normal produce, which varies within comparatively narrow limits, according to the nature of the season, temperature, and other climatic conditions. But the case is completely altered if the crop, in place of being allowed to decay on the soil, is removed from it, for, though the air will continue to afford an undiminished supply of those elements of the food of plants which may be derived from it, the fixed substances, which can only be obtained from the soil, decrease in quantity, and are at length entirely exhausted. In this way a gradual diminution of the fertility of the soil takes place, until, after the lapse of a period, longer or shorter, according to its natural resources, it will become entirely incapable of maintaining a crop, and fall into absolute infertility unless the substances removed from it are restored from some other source in the form of manure. When this is done, the fertility of the soil may not only be sustained but greatly increased, and, in point of fact, all cultivated soils, by the use of manure, are made to yield a much larger crop than they can do in their natural condition.

The fundamental principle upon which a manure is employed is that of adding to the soil an abundant supply of the elements removed from it by plants in the condition best fitted for absorption by their roots; but looked at in its broadest point of view, it acts not merely in this way, but also by promoting the decomposition of the already partially disintegrated rocks of which the soil is composed, setting free those substances it already contains, and facilitating their absorption by the plants.

In considering the practical applications of the broad general principle just stated, it might be assumed that a manure ought invariably to contain all the elements of plants in the quantities in which they are removed by the crops, and that when this has been accurately ascertained by analysis, it would only be necessary to use the various substances in the proportions thus indicated. But this, though a very important, and no doubt in many cases essential condition, is by no means the only matter which requires to be taken into consideration in the economical application of manures. And this becomes sufficiently obvious when the circumstances attending the exhaustion of the soil are minutely examined. When a soil is cropped during a succession of years with the same plant, and at length becomes incapable of longer maintaining it, the exhaustion is rarely, if ever, due to the simultaneous consumption of all its different constituents, but generally depends upon that of one individual substance, which, from its having originally existed in the soil in comparatively small quantity, is removed in a shorter time than the others. To restore the fertility of a soil in this condition, it is by no means necessary to supply all the different substances required by the plant, for it will suffice to add that which has been entirely removed. On the other hand, if an ordinary soil be supplied with a manure containing a very small quantity of one of the elements of plant food, along with abundance of all the others, the amount of increase which it yields must obviously be measured, not by those which are abundant, but by that which is deficient; for the crop which grows luxuriantly so long as it obtains a supply of all its constituents, is arrested as effectually by the want of one as of all, as has been proved by the experiments of Prince Salm Horstmar and others, referred to in a previous chapter; and hence, in order to obtain a good crop, it would be necessary to use the manure in such abundance as to supply a sufficiency of the deficient element for that purpose. If this course were persevered in for a succession of years, the other substances which would have been used in much more than the quantity required by the crops, must either have been entirely lost or have accumulated in the soil. In the latter case it is sufficiently obvious that the soil must have been gradually acquiring an amount of resources which must remain dormant until the system of manuring is changed. To render them available, it is only necessary to add to it a quantity of the particular substance in which the manure hitherto employed has been deficient, so as to restore the lost balance, and enable the plant to make use of those which have been stored up within it. The substance so used is called a special manure; that containing all the constituents of the crop is a general manure.

The distinction of these two classes of manures is very important in a practical point of view, because a special manure is not by itself capable of maintaining the life of plants, but is only a means of bringing into use the natural and acquired resources of the soil. In place of preventing or retarding its exhaustion, it rather accelerates it by causing the increased crops to consume more abundantly, and within a shorter period of time, those substances which it contains. On the other hand, a general manure prevents or diminishes the consumption of the elements of plant-food contained in the soil, and if added in sufficient abundance, may cause them to accumulate in it, and even enable an almost absolutely barren soil to yield a tolerable crop. General manures must therefore always be the most important and essential, and no others would be used if it were possible to obtain them of a composition exactly suited to the requirements of the crop to be raised. Practically, however, this condition cannot be fulfilled, because all the substances available for the purpose, and particularly farm-yard manure, are refuse matters, the exact composition of which is not under our control, and they do not necessarily contain their constituents either in the most suitable proportions, or the most available forms, and consequently when they are used during a succession of years, certain of their constituents may accumulate in the soil, and it is under such circumstances that special manures are both necessary and advantageous.

Several different substances, but more especially farm-yard manure, fulfil in a very remarkable manner the conditions of a general manure, and supply abundantly, not merely the mineral, but also the carbonaceous and nitrogenous matters necessary for building up the organic part of the plant; and hence its use is governed by principles of comparative simplicity, and really resolves itself into determining the best mode of managing it so as effectually to preserve its useful constituents, and, at the same time, to bring them into those forms of combination in which they are most available to the plant. But the employment of a special manure opens up nice questions as to the relative importance of the different elements of plants which have given rise to much controversy and difference of opinion.

In treating of the food of plants, it has been already observed that the fixed or mineral constituents which are contained in their ash, are necessarily derived exclusively from the soil, but that the carbon, hydrogen, nitrogen, and oxygen, of which their organic part is composed, may be obtained either from that source or from the air. The important distinction which thus exists between these two classes of substances, has given rise to two different views regarding the theory of manures. Basing his views on the presence of the organic elements in the air, Liebig has maintained that it is unnecessary to supply them in the manure, while others, among whom Messrs. Lawes and Gilbert have taken a prominent position, hold that, as a rule, fertile soils, cultivated in the ordinary manner, contain a sufficient supply of mineral matters for the production of the largest possible crops, but that the quantity of ammonia and nitric acid which the plants are capable of extracting from the air is insufficient, and must be supplemented by manures containing them. A large number of experiments have been made in support of these views, but the inferences which can be drawn from them are not absolutely conclusive on either side, and it is necessary to consider the matter in a general point of view.

Setting out from the proposition already so frequently referred to, that the plant cannot grow unless it receives a supply of all its elements, it must be obvious that if, to a soil containing a sufficiency of mineral matters to raise a given number of crops, a supply of ammonia be added, its total productive capacity cannot be thus increased; and though it may yield larger crops than it would have done without that substance, this can only be accomplished by a proportionate diminution of their number. In either case, the same quantity of vegetable matter will be produced, but the time within which it is obtained will be regulated by the supply of ammonia. That substance differs in no respect from any other element of plant-food, and used in this way is to all intents and purposes a special manure, and acts merely by bringing into play those substances which the soil already contains. Its effect may not be apparent until after the lapse of a very long period of time, but it ultimately leads to the exhaustion of the soil. If, on the other hand, a soil be continuously cropped until it ceases to yield any produce, it is manifest that the exhaustion must in this instance be entirely due to the removal of its available mineral nutriment, because the superincumbent air constantly changed by the winds must continue to afford the same unvarying supply of the organic elements, and the power of supporting vegetation would be restored to it, by adding the necessary inorganic matters. Hence when a soil, which in its natural condition is capable of yielding a certain amount of vegetable matter, is rendered barren by the removal of the crop, it may be laid down as an incontrovertible position, that its infertility is due to the loss of mineral matters, and that it may be restored to its pristine condition by the use of them, and of them only.

But the case is materially altered when we come to consider the course of events in a cultivated soil. The object of agriculture is to cause the soil, by appropriate treatment, to yield much more than its normal produce, and the question is, how this can be best and most economically effected in practice. According to Liebig, it is attained by adding to the soil a liberal supply of those mineral substances required by the plant, and that it is unnecessary to use any of the organic elements, because they are supplied by the air in sufficient quantity to meet the requirements of the most abundant crops. Other chemists and vegetable physiologists again hold that though a certain increase may be obtained in this way, a point is soon reached beyond which mineral matters will not cause the plant to absorb more ammonia from the air, although a further increase may be obtained by the addition of nitrogen in that or some other available form.

It is admitted on both sides, that all the elements of plant food are equally essential, and the controversy really lies in determining what practically limits the crop producible on any soil. The point at issue may be put in a clear point of view by considering the course of events on a soil altogether devoid of the elements of plants. If a small quantity of mineral matters be added to such a soil, it immediately becomes capable of supporting a certain amount of vegetation, deriving from the air the organic elements necessary for this purpose, and with every increase of the former, the air will be laid under a larger contribution of the latter, to support the increased growth, and this must proceed until the limit of supply from the atmosphere is reached. At this point a further supply of mineral matters alone must obviously be incapable of again increasing the crop, and it would thus be absolutely necessary to conjoin them with a proportionate quantity of organic substances. Liebig maintains that this limit is never attained in practice, but that the air affords ammonia and the other organic elements in excess of the requirements of the largest crop, while mineral matters are generally though not invariably present in the soil in insufficient quantity. Messrs. Lawes and Gilbert, on the other hand, believe that the soil generally contains an excess of mineral matters, and that a manure which is to bring out their full effect must contain ammonia, or some other nitrogenous substance fitted to supplement the deficient supply afforded by the atmosphere. In short, the question at issue is, whether there is or is not a sufficiency of atmospheric food to meet the demands of the largest crop which can practically be produced.

An absolutely conclusive reply to this question is by no means easy. The experiments by which it is to be resolved are complicated by the fact, that all soils capable of supporting anything like a crop, contain not only the mineral, but the organic elements of its food in large and generally in greatly superabundant quantity, and it is impossible satisfactorily to ascertain how much is derived from this source, and how much from the atmosphere. There are in fact no experiments in which the effects of a purely mineral soil have been ascertained. The important and carefully performed researches of Messrs. Lawes and Gilbert were made upon a soil which had been long under cultivation, and contained decaying vegetable matters in sufficient abundance to supply nitrogen to many successive crops, and it would be most unreasonable to assert that the produce they did obtain by means of mineral manures, drew the whole of its nitrogen from the air. On the contrary, it may be fairly assumed that the soil did yield a certain quantity of its nitrogenous compounds, but to what extent this occurs, it is impossible to determine. This difficulty is encountered more or less in all the other experiments, and precludes absolute conclusions. The same fallacy also besets the arguments of Liebig when he holds that the crop, increased by means of mineral manures alone, must derive the whole of the additional quantity of nitrogen which it contains from the air, as appears to be tacitly assumed throughout the whole discussion. So far from this being the case, it is just as likely that the mineral matters should cause the plants to take it from the soil, if it is there, as from the atmosphere.

Taking a general view of the whole question, it is evident that a certain amount of vegetation may always be produced by means of mineral manures, and the quantity obtained is generally much beyond the normal produce of the soil. But it is still open to doubt whether the largest possible crop can be thus obtained, although the balance of evidence is against it, and in favour of the addition of ammonia, and other nitrogenous and organic substances, to the soil. In actual practice manures containing nitrogen are more important, and more extensively applied than any others, and the quantity of that element thus used is very much larger than is generally supposed. Twenty tons of farm-yard manure, a quantity commonly applied, and often exceeded on well cultivated land, contain a sufficiency of organic matters to yield about 2-1/2 cwt. of nitrogen. A complete rotation, according to the six-course shift, contains almost exactly the same quantity of nitrogen, when we assume average crops throughout the whole, and it is thus made up.[K]

Lbs. of Nitrogen. 1. Turnips (13-1/2 tons) 60 2. { Wheat (28 bushels at 60 lbs.) 29 { Straw 16 3. Hay (2-1/2 tons) 56 4. { Oats (34 bushels at 40 lbs.) 27 { Straw 14 5. Potatoes (3 tons) 27 6. Wheat and straw as before 45 —— Total 274

The supply is therefore quite sufficient for the requirements of the crop; and when it is borne in mind that a considerable quantity of ammonia and nitric acid is annually carried down by the rain, and that during a long rotation other substances are very generally used in addition to farm-yard manure, it is obvious that the crop need not depend to any extent upon what it derives from the air. What is true of the nitrogenous matters applies with still greater force to the mineral constituents of the manure. Twenty tons of farm-yard manure contain 32 cwt. of mineral matters, while the average crops of a six course-shift contain only 1088 lbs., or less than one-third of this quantity. It is obvious, therefore, that in well manured land there must be a gradual increase of all the constituents of plants, but that of the mineral matters is relatively much greater than that of the nitrogenous. If therefore from any cause the crop produced on a soil to which farm-yard manure had been applied were greatly to exceed the average, the amount of produce, so far as the soil is concerned, would be limited not by deficiency of mineral, but of nitrogenous food. Hence also when farm-yard manure is liberally applied, there is a gradual accumulation of valuable matters, and a progressive improvement of the productive capacity of the soil.

It is far otherwise, however, if a special manure is employed, because in that case the crop is thrown upon the resources of the soil itself for all its constituents except those contained in the substance employed, and by persisting in its exclusive use exhaustion is the inevitable result. It would be wrong, however, to infer from this, that special manures are to be avoided. On the contrary, great benefits are derived from their judicious employment, and the circumstances under which they are admissible may be readily gathered from what has already been said. They are agents which bring into useful activity the dormant resources of the soil, they restore the proper balance between its different constituents, and supply the excessive demand of some particular elements. Thus, for instance, in a soil containing an abundant supply of mineral matters, a salt of ammonia or nitric acid increases the crop, by promoting the absorption of the substances already present. So likewise a soil on which young cattle and milch cows have been long pastured has its fertility restored by phosphate of lime, because that substance is removed in the bones and milk in relatively much larger proportion than any others.

The choice of a special manure is necessarily dependent on a great variety of circumstances, and is governed partly by the nature of the soil, and partly by that of the crop. It is obvious that cases may occur in which any individual element of the plant may be deficient, and ought to be supplied, but experience has shown that, as a rule, nitrogen and phosphoric acid are the substances which it is most necessary to furnish in this way, and which in all but exceptional cases produce a marked effect on the crop. The other substances, such as potash, soda, magnesia, etc., occasionally act beneficially, but the results obtained from them are very uncertain, and frequently entirely negative.

It has been commonly asserted that phosphates are specially adapted to root crops, and ammonia or nitrates to the cereals, and this statement is so far true, that the former are used with advantage on the turnip, while the latter act with great benefit on grain crops and more especially on oats and barley. The effect of the latter, however, is more or less apparent in all crops and on all soils, because it promotes the assimilation of the mineral matters already present. But its peculiar importance lies in the power which it has of promoting the rapid development of the young plant, causing it to send its roots out into the soil, and to spread its leaves into the air, thus enabling it to take from those two sources, abundance of the useful substances existing in them. But it ought to be distinctly understood, that the statement that particular manures are specially suited to particular crops must be assumed with some reservation, because everything depends upon the nature of the food contained in the soil. It is well known that there are many soils in which ammonia acts more favourably on the turnip than phosphates, and vice versa, and the difference is often due to the previous treatment. In many cases in which ammonia when first used proved most beneficial, it now begins to lose its effect, and the reason no doubt is, that by its means the phosphates existing in these soils have been reduced in amount, while the ammonia has accumulated, so that a change in the system of manuring becomes necessary. A general manure may be used year after year in a perfectly routine manner, but where a special manure is employed, the importance of watching its effects, and altering it as circumstances indicate, cannot be over-estimated. The length of time during which special manures have been extensively used has not been sufficient to bring this prominently before the agriculturist, but its importance must sooner or later force itself upon him, and he will then see the necessity for studying the succession of manures as well as that of crops.

Hitherto we have considered a manure merely as a source from which plants derive their food, but it exercises a scarcely less important action on the chemical and physical properties of the soil. Farm-yard manure, which, as we shall afterwards see, contains a large amount of decomposing vegetable and animal matters, yields a supply of carbonic acid, which operates on the mineral constituents, promotes their further disintegration, and thus liberates their useful elements. It affects also their physical properties, for it diminishes the tenacity of heavy clays; each straw as it decomposes forming a channel through which the roots of plants, air, and moisture can penetrate more readily than through the stiff clay itself. On the other hand, it diminishes the porosity of light sandy soils, causes them to retain moisture, and generally makes their texture more suitable to the plant. Special manures probably act to some extent chemically on the soil, but the nature of the changes they produce is as yet imperfectly understood. Superphosphates which are highly acid in all probability act powerfully on the mineral substances, and common salt, which, though of little importance to the plant, occasionally produces very striking effects, appears to exercise some decomposing action on the soil. It is difficult, however, to trace the mode in which they operate on a substance of such complexity as the soil. Lime, as we shall afterwards see, acts by promoting the decomposition of the vegetable matters on the soil, and possibly some other substances may have a similar effect.

In the application of manures to the soil there are several circumstances which must be taken into consideration. It is generally stated that they ought to be distributed as uniformly as possible, but this is not always necessary nor even advisable, and certainly is not acted on in practice. Much must depend upon the nature both of crop and soil. When the former throws out long and widely penetrating roots, the more uniformly the manure is distributed the better; but if the rootlets are short, it is clearly more advisable that it should be deposited at no great distance from the seed. Practically this is observed in the case of the potato and turnip, which are short rooted, and where the manure is generally deposited close to the seed. But this course is never adopted with the long rooted cereals, the manure being usually applied to the previous crop, so that the repeated ploughings to which the soil is subjected in the interval may distribute what remains as widely and uniformly as possible. In soils which are either excessively tenacious or light, the accumulation of the manure close to the plants has also the effect of producing an artificial soil in their immediate neighbourhood, containing abundance of plant-food, and having physical properties better fitted for the support of the plant. On the other hand, when a special manure is used alone, and with the view of promoting the assimilation of substances already existing in the soil, the more uniform its distribution the better, because it is essential that the roots which penetrate through it should find at every point they reach not only the original soil constituents, but also the substances used to supplement their deficiencies.

FOOTNOTES:

[Footnote K: The quantities here taken are the averages deduced from the agricultural statistics taken in Scotland some years since, with the exception of hay and straw, which are not included in them. I have therefore assumed a reasonable quantity in these cases.]



CHAPTER VIII.

THE COMPOSITION AND PROPERTIES OF FARM-YARD AND LIQUID MANURES.

In the preceding chapter, a general manure has been defined as one containing all the constituents of the crop to which it is to be applied, in a state fitted for assimilation. This condition is fulfilled only by substances derived from the vegetable and animal kingdoms, and most effectually by a mixture of both. On this account, and also because its properties are such as enable it to act powerfully on the soil, farm-yard manure must always be of the highest importance. It is, in fact, the typical manure, and in proportion as other substances approach it in properties and composition, is their value for general purposes on the farm.

Farm-yard manure is a mixture of the dung and urine of domestic animals, with the straw used as litter; and its value and composition must necessarily depend upon that of these substances, as well as on the proportion in which they are mixed. The dung of animals consists of that part of their food which passes through the intestinal canal without undergoing assimilation; the urine containing the portion which has been assimilated and is again excreted, in consequence of the changes which are proceeding in the tissues of the animal. Their composition is naturally very different, and must be separately considered.

Urine.—Urine consists of a variety of earthy and alkaline salts, and of certain organic substances, generally rich in nitrogen, dissolved in a large quantity of water. That of the different domestic animals has been frequently examined, but the analyses of Fromberg give the most complete view of their manurial value:—

Horse. Swine. Ox. Goat. Sheep.

Extractive matter } 2.132 0.142 2.248 0.100 0.340 soluble in water } Extractive matter } 2.550 0.387 1.421 0.454 3.330 soluble in spirit} Salts soluble in } 2.340 0.909 2.442 0.850 1.957 water } Salts insoluble in} 1.880 0.088 0.155 0.080 0.052 water } Urea 1.244 0.273 1.976 0.378 1.262 Hippuric acid 1.260 ... 0.550 0.125 ... Mucus 0.005 0.005 0.007 0.006 0.025 Water 88.589 98.196 91.201 98.007 92.897 ——— ———- ———- ———- ———- 100.000 100.000 100.000 100.000 99.863

Composition of the Ash of these Urines.

Horse. Swine. Ox. Goat. Sheep. Carbonate of lime 12.50 ... 1.07 trace 0.82 Carbonate of magnesia 9.46 ... 6.93 7.3 0.46 Carbonate of potash 46.09 12.10 77.28 trace ... Carbonate of soda 10.33 ... ... 53.0 42.25 Sulphate of potash ... ... 13.30 ... 2.98 Sulphate of soda 13.04 7.00 ... 25.0 7.72 Phosphate of soda ... 19.00 ... ... ... Phosphate of lime } Phosphate of magnesia } ... 8.80 ... ... 0.70 Chloride of sodium 6.94 53.10 0.30 14.7 32.01 Chloride of potassium ... trace ... ... 12.00 Silica 0.55 ... 0.35 ... 1.06 Oxide of iron and loss 1.09 ... 0.77 ... ... ——— ——— ——— ——— ——— 100.00 100.00 100.00 100.00 100.00

Human urine has been accurately examined by Berzelius, although his estimate of the proportion of urea is generally admitted to be above the average. His analysis gives the following numbers:—

Natural. Dry Residue. Urea 3.010 44.70 Lactic acid, lactate of ammonia,} 1.714 25.58 and extractive matter } Uric acid 0.100 1.49 Mucus 0.032 0.48 Sulphate of potash 0.371 5.54 Sulphate of soda 0.316 4.72 Phosphate of soda 0.294 4.39 Biphosphate of ammonia 0.165 2.46 Chloride of sodium 0.445 6.64 Muriate of ammonia 0.150 2.46 Phosphates of magnesia and lime 0.100 1.49 Silica 0.003 0.05 Water 93.300 ———- ——— 100.000 100.00

Among the special organic constituents of the urine are three substances, urea, uric acid, and hippuric acid, which are of much importance in a manurial point of view. The first of these is found in considerable quantity in the urine of all animals, but is especially abundant in the carnivora. Uric acid is found only in these animals, and is the most remarkable constituent of the excrement of birds, serpents, and many of the lower animals. Hippuric acid is most abundant in the herbivora. These substances are all highly nitrogenous. They contain—

Urea. Uric Acid. Hippuric Acid. Carbon 20.00 36.0 60.7 Hydrogen 6.60 2.4 5.0 Nitrogen 46.70 33.4 8.0 Oxygen 26.70 28.2 26.3 ——— ——- ——- 100.00 100.0 100.0

They are extremely prone to change, and in presence of animal matters readily ferment, and are converted into salts of ammonia. Thus human urine, which, at the time of emission is free from smell of ammonia, and has a slightly acid reaction, becomes highly ammoniacal if it be kept for a few days. This is due to the conversion of urea into carbonate of ammonia; and the same change takes place, though more slowly, with uric and hippuric acids.

It is obvious, from the foregoing analyses, that great differences must exist in the manurial value of the urine of different animals. Not only do they vary greatly in the proportion of solid matters which they contain, but also in the kind and quantity of their nitrogenous constituents. They differ also in regard to their saline ingredients; and while salts of potash and soda form the principal part of the ash of the urine of the ox, sheep, goat, and horse, and phosphoric acid and phosphates are entirely absent, that of the pig contains a considerable quantity of the latter substances, and in this respect more nearly resembles the urine of man. Human urine is also much richer in urea and nitrogenous constituents generally, and has a higher value than any of the others.

It is especially worthy of notice that the urine of the purely herbivorous animals (with the exception of the sheep, which contains a small quantity), are devoid of phosphates and urea; and consequently, when employed alone, they are not general manures—a matter of some importance in relation to the subject of liquid manuring, which will be afterwards discussed.

Dung.—The solid excrement of animals is equally variable in composition. That of the domestic animals which had the ordinary winter food was found to have the following composition:—

Horse. Cow. Sheep. Swine. Per-centage of water in the } 77.25 82.45 56.47 77.13 fresh excrement } Ash in the dry excrement 13.36 15.23 13.49 37.17

100 parts of ash contained—

Horse. Cow. Sheep. Swine. Silica 62.40 62.54 50.11 13.19 Potash 11.30 2.91 8.32 3.60 Soda 1.98 0.98 3.28 3.44 Chloride of sodium 0.03 0.23 0.14 0.89 Phosphate of iron 2.73 8.93 3.98 10.55 Lime 4.63 5.71 18.15 2.63 Magnesia 3.84 11.47 5.45 2.24 Phosphoric Acid 8.93 4.75 7.52 0.41 Sulphuric acid 1.83 1.77 2.69 0.90 Carbonic acid ... trace trace 0.60 Oxide of manganese 2.13 ... ... ... Sand ... ... ... 61.37 —— —— —— —— 99.80 99.29 99.64 99.82

Human faeces contain about 75 per cent of water; and their dry residue was found by Way to have the following composition:—

Organic matter 88.52 Insoluble siliceous matters 1.48 Oxide of iron 0.54 Lime 1.72 Magnesia 1.55 Phosphoric acid 4.27 Sulphuric acid 0.24 Potash 1.19 Soda 0.31 Chloride of sodium 0.18 ——— 100.00

In a sample analyzed by myself there were found—

Organic matter 86.75 Phosphates 8.19 Alkaline salts, containing 1.18 of phosphoric } 2.53 acid } Insoluble matters 2.53 ——— 100.00

Nitrogen 4.59 Equal to ammonia 5.57

It is to be observed that the urine and dung of animals differ conspicuously in the composition of their ash, the former being characterized by the abundance of alkaline salts, while the latter contains these substances in small proportion, but is rich in earthy matters, and especially in phosphoric acid. Salts of potash, for example, form nine-tenths of the inorganic part of the urine of the ox, while less than three per cent of that alkali is found in its dung. Phosphoric acid, on the other hand, is not met with in the urine, but forms about ten per cent of the dung. Silica is the most abundant constituent of the dung, but a large proportion of that found on analysis has been swallowed in the shape of grains of sand and particles of soil mechanically mixed with the food, although part is also derived from the straw and grains, which contain that substance in great abundance. The difference in the quantity of nitrogen they contain is also very marked, and is distinctly shown by the following analyses by Boussingault, which give the quantity of carbon, hydrogen, nitrogen, oxygen, and ash in the dung and urine of the horse and the cow in their natural state, and after drying at 212 deg..

- HORSE. COW. - - + Natural. Dry. Natural. Dry. + - - Urine. Dung. Urine. Dung. Urine. Dung. Urine. Dung. - -+ Carbon 4.46 9.56 36.0 38.7 3.18 4.02 27.2 42.8 Hydrogen 0.47 1.26 3.8 5.1 0.30 0.49 2.6 5.2 Nitrogen 1.55 0.54 12.5 2.2 0.44 0.22 3.8 2.3 Oxygen 1.40 9.31 11.3 37.7 3.09 3.54 26.4 37.7 Ash 4.51 4.02 36.4 16.3 4.68 1.13 40.0 12.0 Water 87.61 75.31 0.0 0.0 88.31 90.60 0.0 0.0 + - - 100.00 100.00 100.0 100.0 100.00 100.00 100.0 100.0 - - -

Hence, weight for weight, the urine of the horse, in its natural state, contains three times as much nitrogen as its dung; that of the cow twice as much; and the difference, especially in the horse, is still more conspicuous when they are dry.

It is obvious that the quality of farm-yard manure must depend—1. On the kind of animal from which it is produced; 2. On the quantity of straw which has been used as litter; 3. On the nature of the food with which the animals have been supplied; 4. On the extent to which its valuable constituents have been rendered available by the treatment to which it has been subjected; and 5. On the care which has been taken to prevent the escape of the urine, or of the ammonia produced by its decomposition.

The composition of farm-yard manure has engaged the attention of several chemists; but there are still many points on which our information regarding it is less complete than might be desired. Its investigation is surrounded with peculiar difficulties, not merely on account of its complexity, but because its properties render it exceedingly difficult to obtain a sample which fairly represents its average composition. In the case of long dung, these difficulties are so great that it is scarcely possible to overcome them; and hence, discrepancies are occasionally to be met with in the analyses of the most careful experimenters. The most minute and careful analyses yet made are those of Voelcker, who has compared the composition of fresh and rotten dung, and studied the changes which the former undergoes when preserved in different ways. He employed in his experiments both fresh and rotten dung, and subjected them to different methods of treatment. His analyses are given in the accompanying table, in which column 1 gives the composition of fresh long dung, composed of cow and pig dung. 2. Is dung of the same kind, after having lain in a heap against a wall, but otherwise unprotected from the weather for three months and eleven days in winter, during which time little rain fell. 3. The same manure, kept for the same time under a shed. 4. Well rotten dung, which had been kept in the manure heap upwards of six months. 5. The same, after having lain against a wall for two months and nine days longer.

+ -+ -+ -+ + 1 2 3 + -+ -+ -+ + Water 66.17 69.86 67.32 Soluble organic matters 2.48 3.86 2.63 Soluble inorganic matters. Silica 0.237 0.279 0.239 Phosphate of lime 0.299 0.300 0.331 Lime 0.066 0.048 0.056 Magnesia 0.011 0.019 0.004 Potash 0.573 1.096 0.676 Soda 0.051 0.187 0.192 Chloride of sodium 0.030 0.106 0.058 Sulphuric acid 0.055 0.160 0.119 Carbonic acid and loss 0.218 0.775 0.445 - 1.54 ... 2.97 - 2.12 Insoluble organic matters 25.76 18.44 20.46 Insoluble inorganic matters Soluble silica 0.967 0.712 1.893 Insoluble silica 0.561 0.857 1.075 Oxide of iron, alumina, and phosphates 0.596 0.810 1.135 + -+ -+ -+ +

- - - 4 5 - - - Water 75.42 73.90 Soluble organic matters 3.71 2.70 Soluble inorganic matters Silica 0.254 0.147 Phosphate of lime 0.382 0.129 Lime 0.117 0.018 Magnesia 0.047 0.018 Potash 0.446 0.960 Soda 0.023 0.082 Chloride of sodium 0.037 0.052 Sulphuric acid 0.058 0.072 Carbonic acid and loss 0.106 0.584 - 1.47 - 2.06 Insoluble organic matters 12.82 14.39 Insoluble inorganic matters Soluble silica 1.424 1.10 Insoluble silica 1.010 1.54 Oxide of iron, alumina, and phosphates 0.947 0.37 - - -

+ -+ -+ -+ + 1 2 3 + -+ -+ -+ + Containing phosphoric acid (0.178) (0.177) (0.298) Equal to bone earth (0.386) (0.277) (0.646) Lime 1.120 1.291 1.868 Magnesia 0.143 1.029 0.078 Potash 0.099 0.127 0.208 Soda 0.019 0.046 0.038 Sulphuric acid 0.061 0.099 0.098 Carbonic acid and loss 0.484 0.929 1.077 - 4.05 - 4.90 - 7.47 - - 100.00 100.00 100.00 Containing nitrogen 0.149 0.270 0.170 Equal to ammonia 0.181 0.320 0.206 Containing nitrogen 0.494 0.470 0.580 Equal to ammonia 0.599 0.570 0.700 Total nitrogen 0.643 0.740 0.750 Equal to ammonia 0.780 0.890 0.906 + -+ -+ -+ +

- - - 4 5 - - - Containing phosphoric acid (0.274) (0.06) Equal to bone earth (0.573) (0.10) Lime 1.667 2.25 Magnesia 0.091 0.02 Potash 0.045 0.12 Soda 0.038 0.01 Sulphuric acid 0.063 0.10 Carbonic acid and loss 1.295 1.44 - 6.58 6.95 - 100.00 100.00 Containing nitrogen 0.297 0.149 Equal to ammonia 0.360 0.180 Containing nitrogen 0.309 0.613 Equal to ammonia 0.375 0.744 Total nitrogen 0.606 0.762 Equal to ammonia 0.735 0.924 - - -

On examining and comparing these analyses, it appears that the differences are by no means great, although, on the whole, they tend to show that, weight for weight, well-rotten dung is superior to fresh, provided it has been properly treated. Not only is the quantity of valuable matters existing in the soluble state materially increased, whereby the dung is enabled to act with greater rapidity, but, owing to evaporation and the escape of carbonic acid, produced by the decomposition of the organic substances, the proportion of those constituents which are most important to the plant is increased. This is particularly to be noticed, in regard to the nitrogen, which has distinctly increased in all cases in which the dung has been kept for some time; and the practical importance of this observation is very great, because it has been commonly supposed that, during the process of fermentation, ammonia is liable to escape into the air. It would appear, however, that there is but little risk of loss in this way, so long as the dung-heap is left undisturbed; and it is only when it is turned that any appreciable quantity of ammonia volatilizes. It is different, however, with the action of rain, which soon removes, by solution, a considerable quantity of the nitrogen contained in farm-yard manure; and the deterioration must necessarily be most conspicuous in rotten dung, which sometimes contains nearly half of its nitrogen in a soluble condition. The effect produced in this way is conspicuously seen, by the results of weighings and analyses of small experimental dung-heaps, made by Dr. Voelcker at different periods. The subjoined table shows the composition of the heap, lying against a wall, and exposed to the weather at different periods:—

+ + -+ WHEN PUT UP. + -+ + -+ + Nov 3d April 30th Aug 23d Nov 15th 1854. 1855. 1855. 1855. + -+ + -+ + Weight of manure in lbs. 2838 2026 1994 1974 + -+ + -+ + Water 1877.9 1336.1 1505.3 1466.5 Dry Matter 960.1 689.9 488.7 507.5 + -+ + -+ Consisting of Soluble organic matter 70.38 86.51 58.83 54.04 " mineral matter 43.71 57.88 39.16 36.89 Insoluble organic matter 731.07 389.74 243.22 214.92 " mineral matter 114.94 155.77 147.49 201.07 + -+ + -+ + Total nitrogen 18.23 18.14 13.14 13.03 Equal to ammonia 22.14 22.02 15.96 15.75 + + -+ + -+ +

In this case, during the winter six months, which were very dry, the manure lost 541.8 lbs. of water and 270.2 lbs. of dry matter, but the nitrogen remained completely unchanged. But during the succeeding semi-annual period, when rain fell abundantly, the quantity of nitrogen is diminished by nearly a third, while the water has increased, and the loss of dry matter by fermentation, notwithstanding the high temperature of the summer months, was only 182.4 lbs. The soluble mineral matters also, which increased during the first period, are again reduced during the second, until they also fall to about two-thirds of their maximum quantity. That this effect is to be attributed to the solvent action of rain is sufficiently obvious, from a comparison of the results afforded by the other heaps, which had been kept under cover during the same period, as shown below.

+ + WHEN PUT UP. + + + + -+ Nov. 3d, April 30th Aug. 23d Nov. 15th 1854. 1855. 1855. 1855. + + + + -+ Weight of manure in lbs. 3258 1613 1297 1235 + + + + - Water 2156.0 917.6 563.2 514.5 Dry Matter 1102.0 695.4 733.8 720.5 + + + + - Consisting of Soluble organic matter 80.77 74.68 53.56 66.28 " mineral matter 50.14 54.51 39.55 54.68 Insoluble organic matter 839.17 410.24 337.32 341.97 " mineral matter 131.92 155.97 303.37 257.57 + + + + -+ Total nitrogen 20.93 19.26 16.54 1.79 Equal to ammonia 25.40 23.33 20.08 2.81 + + + + + -+

The loss of nitrogen is here comparatively trifling, and during the whole year, but little exceeds two pounds, of which the greater part escapes during the first six months, and the soluble inorganic matters are almost unchanged. The total weight of the manure, however, undergoes a very great reduction, due chiefly to evaporation of water, but in part also to the loss of organic matters evolved in the form of carbonic acid during fermentation.

When the manure is spread out, as it is usually found under cattle in open yards, the deterioration is very great, a quantity thus treated having lost, in the course of a year, nearly two-thirds of its nitrogen, and four-fifths of its soluble inorganic matters.

The general conclusion deducible from these analyses is that, provided it be carefully prepared, farm-yard manure does not differ very largely in value, although the balance is in favour of the well-rotten dung. This result is in accordance with that obtained by other experimenters, who have generally found from 0.5 to 0.6 per cent of nitrogen, and 1 or 2 per cent of phosphates. But when carelessly managed, it may fall greatly short of this standard, as is particularly seen in a sample examined by Cameron, which had been so effectually washed out by the rain, as to retain only 0.15 per cent of ammonia. These cases, however, are exceptional, and well made and well preserved farm-yard manure will generally be found to differ comparatively little in value; and when bought at the ordinary price, the purchaser, as we shall afterwards more particularly see, is pretty sure to get full value for his money, and the specialities of its management are of comparatively little moment to him. But the case is very different when the person who uses the manure has also to manufacture it. The experiments already quoted have shown that, though the manure made in the ordinary manner may, weight for weight, be as valuable as at first, the loss during the period of its preservation is usually very large, and it becomes extremely important to determine the mode in which it may be reduced to the minimum.

In the production of farm-yard manure of the highest quality, the object to be held in view is to retain, as effectually as possible, all the valuable constituents of the dung and urine. But in considering the question here, it will be sufficient to refer exclusively to its nitrogen, both because it is the most important, and also because the circumstances which favour its preservation are most advantageous to the other constituents. In the management of the dung-heap, there are three things to be kept in view:—First, To obtain a manure containing the largest possible amount of nitrogen; secondly, To convert that nitrogen more or less completely into ammonia; and thirdly, To retain it effectually.

As far as the first of these points is concerned, it must be obvious that much will depend on the nature and quantity of the food with which the animals yielding the dung are supplied, and the period of the fattening process at which it is collected. When lean beasts are put up to feed, they at first exhaust the food much more completely than they do when they are nearly fattened, and the manure produced is very inferior at first, and goes on gradually improving in quality as the animal becomes fat.

When the food is rich in nitrogenous compounds, the value of the manure is considerably increased. It has been ascertained, for instance, that when oil-cake has been used, not less than seven-eighths of the valuable matters contained in it reappear in the excrements; and as that substance is highly nitrogenous, the dung ought, weight for weight, to contain a larger amount of that element. That it actually does so, I satisfied myself by experiments, made some years since, when the dung and urine of animals fed on turnips, with and without oil-cake, were examined; but unfortunately, no determination of the total quantity of the excretions could be made, so that it was impossible to estimate the increased value. It has been commonly supposed that when cattle are fed with oil-cake, the increased value of the manure is equal to from one-half to two-thirds the price of the oil-cake; but this is a rather exaggerated estimate as regards linseed-cake, although it falls short of the truth in the case of rape, as we shall afterwards more particularly see.

Although it may be possible, in this way, to increase the quantity of nitrogen as a manure, there is a limit to its accumulation, due to the fact, that it is contained most abundantly in the urine, which can only be retained by the use of a sufficient supply of litter. Where that is deficient, the dung-heap becomes too moist, and the fluid and most valuable part drains off, either to be lost, or to be collected in the liquid manure-tank. In the well managed manure-heap, the quantity of litter should be sufficient to retain the greater part of the liquid manure, and to admit of only a small quantity draining from it, which should be pumped up at intervals, so as to keep the whole in a proper state of moisture. Attention to this point is of great moment, and materially affects the fermentation. When it is too moist or too dry, that process is equally checked; in the former case by the exclusion of air, which is essential to it; and in the latter, by the want of water, without which the air cannot act. The exact mode in which the manure is to be managed must greatly depend on whether the supply of litter is large or small. In the latter case the urine escapes, and is collected in the liquid manure-tank, and must be used by irrigation, and in some cases this mode of application has advantages, but in general, it is preferable to avoid it, and have recourse to substances which increase the bulk of the heap sufficiently to make it retain the whole of the liquid. For this purpose, clay, or still better, the vegetable refuse of the farm, such as weeds, ditch cleanings, leaves, and, in short, any porous matters, may be used. But by far the best substance, when it can be obtained, is dry peat, which not only absorbs the fluid, but fixes the ammonia, by converting it more or less completely into humate. Reference has been already made to the absorbent power of peat in the section on soils, but it may be mentioned here that accurate experiment has shown that a good peat will absorb about 2 per cent[L] of ammonia, and when dry will still retain from 1 to 1.5 per cent, or nearly twice as much as would be yielded by the whole nitrogen of an equal weight of farm-yard manure. Peat charcoal has been recommended for the same purpose, but careful experiment has shown that it does not absorb ammonia, although it removes putrid odour; and though it may be usefully employed when it is wished to deodorize the manure heap, it must not be trusted to for fixing the ammonia.

Much stress has frequently been laid on the advantage to be derived from the use of substances capable of combining chemically with the ammonia produced during the fermentation of dung and gypsum, sulphate of iron, chloride of manganese, sulphate of magnesia, and sulphuric acid, have been proposed for this purpose, and have been used occasionally, though not extensively. They all answer the purpose of fixing the ammonia, that is, of preventing its escaping into the air; but the risk of loss in this way appears to have been much exaggerated, for a delicate test-paper, held over a manure-heap, is not affected; and during fermentation, humic acid is produced in such abundance, as to combine with the greater part of the ammonia. The real source of deterioration is the escape of the soluble matters in the drainings from the manure-heap, which is not prevented by any of these substances; and where no means are taken to preserve or retain this portion, the loss is extremely large, and amounts, under ordinary circumstances, to from a third to a half of the whole value of the manure. Manure, therefore, cannot be exposed to the weather without losing a proportion of its valuable matters, depending upon the quantity of rain which falls upon it. Hence it is obvious that great advantage must be derived, especially in rainy districts, from covered manure-pits. This plan has been introduced on some farms with good effect; but the expense and doubts as to the benefits derived from it, have hitherto prevented the practice becoming general. The principal difficulty experienced in the use of the covered dung-pit is, that, where the litter is abundant, the urine does not supply a sufficiency of moisture to promote the active fermentation of the dung, and it becomes necessary to pump water over it at intervals; but when this is properly done, the quality of the manure is excellent, and its valuable matters are most thoroughly economized.

Although covered dung-pits have been but little used, their benefits have been indirectly obtained by the method of box-feeding, one of the great advantages of which is held to be the production of a manure of superior quality to that obtained in the old way. In box-feeding none of the dung or urine is removed from under the animals, but is trampled down by their feet, and new quantities of litter being constantly added, the whole is consolidated into a compact mass, by which the urine is entirely retained. Whatever objection may be taken to this system, so far as the health of the animals is concerned, there is no doubt as to the complete economy of the manure, provided the quantity of litter used be sufficient to retain the whole of the liquid. But its advantage is entirely dependent on the possibility of fulfilling this condition.

Whether box manure is really superior to that which can be prepared by the ordinary method is very questionable, but it undoubtedly surpasses a large proportion of that actually produced. It is more than probable, however, that the careful management of the manure-heap would yield an equally good product. It is manifest that the same number of cattle, fed in the same way, on the same food, and supplied with the same quantity of litter, must always excrete the same quantities of valuable matters; and the only question to be solved is, whether they are more effectually preserved in the one way than the other? It will be readily seen that this cannot be done by analysis alone, but that it is necessary to conjoin with it a determination of the total weight of manure produced; for though, weight for weight, box manure may be better than ordinary farm-yard manure, the total quantity obtained by the latter method, from a given number of cattle, may be so much greater, that the deficiency in quality may be compensated for. At the present time our knowledge is too limited to admit of a definite opinion on this subject, but it is highly deserving of the combined investigation of the farmer and the chemist.

Supposing the conditions which produce the manure containing the largest quantity of nitrogen to have been fulfilled, we have now to consider those which affect its evolution in the form of ammonia. This change is effected by fermentation. When a quantity of manure is left to itself it becomes hot, and gradually diminishes in bulk, and if it be turned over after some time, the smell of ammonia may be more or less distinctly observed. This ammonia is produced, in the first instance, from the urine, the nitrogenous constituents of which are rapidly decomposed, and the fermentation thus set up in the mass of manure extends first to the solid dung, and then to the straw of the litter, and gradually proceeds until a large quantity of ammonia is produced.

When fresh manure is deposited in the soil, the same changes occur, but they then proceed more slowly, and experience has shown that a much smaller effect is produced on the crop to which it has been applied than when it has been well fermented in the heap. This effect is consistent with theory, which would further indicate that well-fermented dung must be especially advantageous when applied to quick-growing crops, and less necessary to those which come slowly to maturity. As a rule, well fermented manure is to be preferred, provided it has been well managed and carefully prepared; but when this has not been done, and the manure has been exposed to the weather, or made in open courts or hammels, the economic advantages are all on the side of the fresh dung. It may be questioned also whether, now that there are so many other available sources of ammonia, it may not in many instances be advantageous to use the dung fresh, conjoined with a sufficient quantity of some salt of ammonia, or other substance fitted to supply the quantity of that element necessary for the requirements of the crop.

After the farm-yard manure has been prepared at the homestead, it is often necessary to cart it out to the field some time before it is to be applied, and it is a question of some importance to determine how it may be best preserved there. The general practice is to store it in heaps in the corners of the fields, but some difference of opinion exists as to whether it should be lightly thrown up so as to leave it in a porous state, and so promote its further fermentation, or whether it should be consolidated as much as possible by driving the carts on to the top of the heap during its construction. Considering the risks to which the manure is exposed on the field, the latter plan would appear to be the best. It is advisable also to interstratify the dung with dry soil, so as to absorb any liquid which may tend to escape from it, and it should also be covered with a well-beaten layer of earth, in order to exclude the rain. Although these precautions must not be omitted if the manure is to be stored in heaps, it will probably be often found quite as advantageous to spread it at once, and leave it lying on the surface until it is convenient to plough it. The loss of ammonia by volatilization will, under such circumstances, especially in the cold season of the year, be very trifling, and the rain which falls will only serve to incorporate the soluble matters with the soil, where they will be retained by its absorptive power.

In the actual application of the manure to the crop, several points require consideration. It is especially important to determine whether it ought to be uniformly distributed through the soil, or be kept near the roots of the plants. Both systems have their advocates, and each has advantages in particular cases. The choice between the two must greatly depend upon the nature of the crop and the soil. When the former is of a kind which spreads its roots wide and deep through the soil, the more uniformly the manure can be distributed the better; but when it is used with plants whose roots do not travel far, it is more advantageous to accumulate it near the seeds. Obvious advantages also attend this practice in soils which are either too heavy or too light. When, for example, it is necessary to cultivate turnips in a heavy clay, the manure put into the drills produces a kind of artificial soil in the neighbourhood of the plants, in which the bulbs expand more readily than in the clay itself. On the other hand, when a large quantity of dung, in a state of active fermentation, comes into immediate contact with the roots, its effect is not unfrequently injurious. These and many other points, which will readily suggest themselves to any one who studies the composition and properties of farm-yard manure, belong more strictly to the subject of practical agriculture, and need not be enlarged on here.

In the present state of agriculture, a proper estimate of the money value of farm-yard manure is of much importance in an economic point of view, and many matters connected with the profitable management of a farm must hinge upon it. If an estimate be made upon the principle which will be explained when we come to treat of artificial manures, it appears that fresh farm-yard manure of good quality is worth from 12s. to 15s. per ton, and well-rotted dung rather more. It is questionable, however, whether the system of valuation which is accurate in the case of a guano or other rapidly acting substance, is applicable to farm-yard manure, the effects of which extend over some years. A deduction must be made for the years during which the manure remains unproductive, and also for the additional expense incurred in carting and distributing a substance so much more bulky than the so-called portable manures, and it would not be safe to estimate its value at more than 7s. or 8s. per ton.

Liquid Manure.—This term is applied to the urine of the animals fed on the farm, and to the drainings from the manure-heap, which, in place of being returned to it, are allowed to flow away, and collected in tanks, from which they are distributed by a watering-cart, or according to the method recently introduced in Ayrshire, and since adopted in other places, by pipes laid under-ground in the fields, and through which the manure is either pumped by steam-power, or, where the necessary inclination can be obtained, is distributed by gravitation. That liquid manure must necessarily be valuable, is an inference which maybe at once drawn from the analyses of the urine of different animals already given, and of which it chiefly consists. In addition to the urine, however, it contains also the soluble organic and mineral matters of the dung, as well as a quantity of solid matters in suspension, among which phosphates are found, and thus it possesses a supply of an element which would be almost entirely deficient if it were composed of urine alone. In the following analyses by Professor Johnston, No. 1 is the drainings of the manure-heap when exposed to rain; and No. 2 the same, when moistened with cows' urine pumped over it, the results being expressed in grains per gallon:—

No. 1. No. 2. Ammonia 9.6 21.5 Organic matter 200.8 77.6 Ash 268.8 518.4 ——- ——- Total solids in a gallon 479.2 617.5

The ash contained—

Alkaline salts 207.8 420.4 Phosphates 25.1 44.5 Carbonate of lime 18.2 31.1 Carbonate of magnesia, and loss 4.3 3.4 Silica and alumina 13.4 19.0 ——- ——- 268.8 518.4

More elaborate analyses of the same fluid have since been made by Dr. Voelcker, with the subjoined results per gallon:—

1. 2. 3. Organic matters and ammoniacal } 263.80 250.63 70.121 salts } Silica 2.49 9.98 1.154 Oxide of iron 0.70 0.68 ... Lime 5.34 25.18 13.011 Magnesia 2.96 15.33 1.660 Potash 103.23 112.26 13.411 Chloride of potassium 72.00 77.38 7.712 Chloride of sodium 17.18 46.03 17.258 Phosphoric acid 2.70 9.51 2.304 Sulphuric acid 22.31 37.60 3.408 Carbonic acid, and loss 33.90 27.95 14.025 ——— ——— ———- Total solids 526.61 612.53 144.064 Ammonia 114.16 22.31 26.647

The differences are here very remarkable, especially in the quantity of ammonia, which is exceedingly large in the first sample. All of them are particularly rich in potash, and contain but a small proportion of phosphoric acid. The general inference to be deduced from them is, that liquid manure is a most important source of the alkalis and ammonia, and must be peculiarly valuable on soils in which these substances are deficient.

The system of liquid manuring, originally introduced by Mr. Kennedy of Myremill, Ayrshire, and which has since been adopted in some other places, differs from liquid manuring in its strict sense, for not only are the drainings of the manure-heap employed, but the whole solid excrements are mixed with water in a tank, and rape-dust and other substances occasionally added, and distributed through the pipes.

It has been abandoned on Mr. Kennedy's farm, but is in use at Tiptree Hall, and on the farm of Mr. Ralston, Lagg, where the fluid is distributed by gravitation.

The arrangements employed by Mr. Mechi are identical with those formerly in use at Myremill. The greater part of the stock is kept on boards, and the liquid and solid excrements are collected together in the tank, and largely diluted before distribution. The liquid from the tanks has been recently examined by Dr. Voelcker, who found it to contain per gallon—

Organic matter and ammoniacal salts 53.03 Soluble silica 6.47 Insoluble siliceous matter (clay) 15.17 Oxide of iron and alumina 2.36 Lime 6.60 Magnesia 1.73 ——- Potash 0.35 Chloride of potassium 1.95 Chloride of sodium 4.81 Phosphoric acid 3.72 Sulphuric acid 1.94 Carbonic acid, and loss 0.47 ——- Total solids 96.60 Ammonia 8.10

The quantity of this liquid distributed per acre is about 50,000 gallons, at a cost of 2d. per gallon. As this quantity contains about 39 lbs. of ammonia, it must be nearly equivalent to 2 cwt. of Peruvian guano, which costs, with the expense of spreading, from 28s. to 30s. per acre, while the cost of distributing the liquid exceeds L1: 17s. per acre. On the other hand, the rapidity with which liquid manure produces its effect must be taken into account. It is on this that its chief value depends, and especially when applied to grass land in early spring, it produces an abundant crop just when turnips and other winter food are exhausted. Mr. Telfer, Cunning Park, who has used this system for a good many years, has come to the conclusion that it is only in this way that it can be made profitable; and though pipes are laid all over his farm, he has latterly restricted the use of the liquid manure entirely to Italian ryegrass. Its effect on the cereals is much less marked, and it can scarcely be considered as capable of advantageous application to the general operations of the farm. Neither can liquid manure be applied to all soils. It fails entirely on heavy clays, but is peculiarly adapted to light sandy soils; and even barren sand may by its repeated application, be made to yield luxuriant crops. It is not likely that the system of liquid manuring will extend, except in localities where it is possible to distribute it by gravitation; and even then, it will probably be found most economical to restrict its use to one portion of the farm; and for that purpose, the poorest and most sandy soil ought to be selected.

Sewage Manure.—The use of the sewage of towns as a manure is closely connected with that of the liquid manure produced on the farm. Its application must take place in a similar manner, and be governed by the same principles. Although numerous attempts have been made to convert it into a solid form, or to precipitate its valuable matter, none of them have succeeded; nor can it be expected that any plan can be devised for the purpose, because the most important manurial constituents are chiefly soluble, and cannot be converted into an insoluble state, or precipitated from their solution. In its liquid form, however, sewage manure has been employed with the best possible effect in the cultivation of meadows. The most important instance of its application is in the neighbourhood of Edinburgh, where 325 acres receive the sewage of nearly half the town, and have been converted from barren sand into land which yields from L20 to L30 per acre. The contents of the sewer, taken just before it flows into the first irrigated meadow, near Lochend, were found to contain per gallon—

Soluble organic matter 21.90 Insoluble organic matter 21.70 Peroxide of iron and alumina 2.01 Lime 10.50 Magnesia 2.00 Sulphuric acid 6.09 Phosphoric acid 6.14 ——- Chlorine 12.20 Potash 2.89 Soda 13.27 Silica 6.50 ——— 105.20 Ammonia 14.90

It is interesting to notice that this sewage is superior in every respect to the liquid manure used at Tiptree Hall; and the good effects obtained from its application, in the large quantities in which it is used in the Craigentinny meadows, may be well imagined. It operates, not merely by the substances which it holds in solution, but also by depositing a large quantity of matters carried along in suspension, and is in reality warping with a substance greatly superior to river-mud. A deposit collected in a tank, where the sewage passes through a farm, is used as a manure, and contains—

Peroxide of iron and alumina 4.45 Lime 1.74 Magnesia 0.39 Potash 0.10 Soda 0.06 Phosphoric acid 1.08 Sulphuric acid 0.16 Organic matter 17.95 Sand 20.51 Water 53.56 ——— 100.00 Ammonia 0.93

And even, though containing more than half its weight of water and 20 per cent of sand, this substance has considerable value as a manure.

The growing evils of the existing system of sewage, and the enormous waste of a manurial matter, which the experience of the Craigentinny meadows has shewn to be productive of the most important effects, has recently directed much attention to the conversion of the contents of our sewers into a useful manure. Numerous plans for its precipitation and conversion into a solid manure have been proposed, but most of these have shewn an entire ignorance of the fundamental principles of chemistry, and the best only succeed in precipitating a very small proportion of its valuable matters, and leave almost the whole of the ammonia, as well as the greater part of the fixed alkalies, in solution. Nor is it to be expected that any process will be discovered by which these substances can be precipitated, because solubility is the special characteristic of their compounds, and no means is known by which it is possible to convert them into an insoluble form. If sewage is to be used at all, there seems little doubt that it must be by applying it entire, and in the liquid state. But here again, the expense of conveying it on to the land becomes an obstacle which it must frequently be impossible to overcome. When it can be conveyed by gravitation, as is the case in the neighbourhood of Edinburgh, it may undoubtedly be used with the utmost advantage, and with the very best economic results. But when it requires to be carried to a great distance through pipes, and raised to a high level by pumping, all these advantages disappear. If the cost of application amounts to 2d. a gallon, as in Mr. Mechi's case, or even to half that sum, it may be fairly concluded that it cannot be used with any great prospect of large economic results, and that, unless under very exceptional cases, it must be unprofitable.

The chances of success must also greatly depend upon the kind of soil on which it is used. Experience has shewn that its effects are most beneficial on light and deep sandy soils, but that on heavy retentive clays it is without effect, or even absolutely injurious. In clay soils it is important to use every means of getting rid of moisture, and any plan which adds 200 or 300 tons of water to them, only aggravates their natural defects to an extent which more than counterbalances the benefits derived from the manurial matter it contains. Whatever the ultimate result of the use of town sewage in the liquid form may be, it is unlikely that it will be employed in general agricultural practice. It is more probable that it will be found necessary to set apart a certain breadth of land to be treated by it exclusively. Many plans have been proposed for conveying it through considerable districts, and selling to the surrounding farmers the quantities which they require, but wherever large sewage-works are established, it will be impossible to depend on a precarious demand, and the promoters of such schemes will be compelled, as part of their speculation, to supply not only the manure, but the land on which it is to be used. Indeed, the difficulties attending the whole question are so formidable, that even those who are most anxious to see a stop put to the waste of manurial matter must admit that the prospect of a successful economic result is not encouraging. Nor is it likely that anything will be done until the whole system of managing town refuse is changed, and in place of deluging it with water, some plan can be contrived which, while fulfilling sanatory requirements, shall preserve it in a concentrated form, or convert it into a dry and inodorous substance.

FOOTNOTES:

[Footnote L: Report on the economic uses of peat. Highland Society's Transactions, N.S., vol. iv. p. 549.]



CHAPTER IX.

COMPOSITION AND PROPERTIES OF VEGETABLE MANURES.

Many vegetable substances have been employed as manures, either alone or as auxiliaries to farm-yard manure. Like that substance, they are general manures, and contain all the constituents of ordinary crops; but, owing to the absence of animal matter, they in general undergo decomposition and fermentation much more slowly, although some of them contain a so largely preponderating proportion of nitrogen, that they may in some respects be compared to the strictly nitrogenous manures.

Rape-dust, Mustard, Cotton and Castor Cake.—Rape-dust has long been employed as a manure, and the success which has attended its use has led to the introduction of the refuse cake from some other oil seeds, such as those of mustard and castor-oil, which cannot be employed for feeding. Like the seeds of all plants, these substances are rich in nitrogen, and their ash, containing of course all the constituents of the plant, supplies the necessary inorganic elements. The following are analyses of these substances, which, in addition to the amount of nitrogen and phosphates, shew also that of water and oil, to which reference will be made in a future chapter, in relation to the feeding value of some of them. The detailed composition of their ash may be judged of from that of the seeds from which they are made, and which have been given under that head.

- - - Rape-Cake. Poppy-Cake. Cotton-seed Castor- Cake. Cake. - - -+ Water 10.68 11.63 11.19 12.31 Oil 11.10 5.95 9.08 24.32 Albuminious } 29.53 31.16 25.16 21.91 compounds } Ash 7.79 12.98 5.64 6.08 Other constituents 40.90 38.18 48.93 35.38 + - - - 100.00 100.00 100.00 100.00 Nitrogen 4.38 4.94 3.95 3.20 Silica 1.18 3.36 1.32 1.96 Phosphates 3.87 69.3 2.19 2.81 Phosphoric acid } in combination } 0.39 3.27 0.15 0.64 with alkalies } - - -

A general similarity may be observed in the composition of all these substances; they are rich in nitrogen, and contain as much of that element as is found in six or seven times their weight of farm-yard manure, and a somewhat similar proportion exists in the amount of phosphates, and probably of their other constituents. They have all been employed with success, but the most accurate observations have been made with rape-dust, which has been longer and more extensively used than any of the others. It has been employed alone for turnips, or mixed with farm-yard manure, and also as a top-dressing to cereals. But the most marked advantage is derived from it when applied in the latter way on land which has been much exhausted, and its effects are then very striking. An adequate supply of moisture is essential to the production of its full effects, and hence it often proves a failure in very dry seasons, and on dry soils. It must not be applied in too great abundance, experience having shewn that after a certain point has been reached, an increase in the quantity produces no benefit, and even sometimes positively diminishes the crop. The other substances of the same class, in all probability, act in the same way, but as their introduction is recent, and their use limited, less is known regarding their effects.

Malt-Dust, Bran, Chaff, etc.—The value of these substances as manures is chiefly dependent on the nitrogen they contain, though to some extent also on their inorganic constituents. Malt-dust contains about 4.5 per cent, and bran 3.2 per cent of nitrogen. But they are little used as manures, as they can generally be more advantageously employed for feeding. The value of chaff more nearly resembles that of straw.

Straw is occasionally employed as a manure, and sometimes even as a top-dressing for grass land. It is generally admitted, however, that its application in the dry state, and especially as a top-dressing, is a practice not to be recommended, as it decomposes too slowly in the soil; and it is always desirable to ferment it in the manure heap, so as to facilitate the production of ammonia from its nitrogen. Still circumstances may occur in which it becomes necessary to employ it in the dry state, and it will generally prove most valuable on heavy soils, which it serves to keep open, and so promotes the access of air, and enables it to act on the soil. On light sandy soils it generally proves less advantageous, as its tendency of course is to increase the openness of the soil, and render it less able to retain the essential constituents of the plant.

The quantity of nitrogen in straw does not exceed 0.2 per cent, and its value is mainly due to its inorganic constituents and to its mechanical effect on the soil.

Saw-dust has little value as a manure, as it undergoes decomposition with extreme slowness. It is a good mechanical addition to heavy soils, and diminishes their tenacity; and though its manurial effects are small, it sooner or later undergoes decomposition, and yields what valuable matters it contains. The saw-dust of hard wood is to be preferred, both because it contains more valuable matters than that of soft wood, and because the absence of resinous matters permits its more rapid decomposition. It is a useful absorbent of liquid manure, and may be advantageously added to the dung-heap for that purpose.

Manuring with Fresh Vegetable Matter—Green Manuring.—The term green manuring is applied to the system of sowing some rapidly growing plant, and ploughing it in when it has attained a certain size, and the success attending it, especially on soils poor in organic matters, is very marked. It is obvious that this mode of manuring can add nothing to the mineral matters contained in the soil, and its utility must therefore be due to the plant gathering organic matters from the air, which, by their decomposition, yield nitrogen and carbonic acid—the former to be directly made use of by subsequent crops, the latter, in all probability, acting also on the soil, and setting free its useful constituents. Hence those plants which obtain the largest quantity of their organic elements from the air ought to be most advantageous for green manuring. The plants used for this purpose act also as a means of bringing up from the lower parts of the soil the valuable matters which exist in it out of reach of ordinary crops, and mixing them again with the surface part. Many of the plants found most useful for green manuring send down their roots to a considerable depth; and when they are ploughed in, all the substances which they have brought up are of course deposited in the upper few inches of the soil. Vegetable matter when ploughed in in the fresh state, also decomposes rapidly, and is therefore able immediately to improve the subsequent crop; and as this decomposition takes place in the soil without the loss of ammonia and other valuable matters, which is liable to occur to a greater or less extent when they are fermented on the dung-heap, it will be obvious that in no other mode can equally good results be obtained by its use.

Many plants have been employed as green manure, and different opinions have been expressed as to their relative values. In the selection of any one for the purpose, that should of course be taken which grows most rapidly, and produces within a given time the largest quantity of valuable matters, but no general rule can be given for the selection, as the plant which fulfils those conditions best will differ in different soils and climates. The plants most commonly employed in this country are spurry, white mustard, and turnips. Rye, clover, buckwheat, white lupins, rape, borage, and some others, have been largely employed abroad. Some of these are obviously unfitted for the climate of the British Islands; and the others, although they have been tried occasionally, do not appear to have been very extensively employed. The turnip is sown broadcast at the end of harvest, and ploughed in after two months. White mustard and spurry are employed in the same way as a preparation for winter wheat, and with the best results. The latter is sometimes sown as a spring crop in March, ploughed in in May, and another crop sown which is ploughed in in June, and immediately followed by a third. The effect of this treatment is such that the worst sands may be made to bear a remunerative crop of rye.