1902 Encyclopedia > Manure

Manure




MANURE. The term " manure," though formerly ap-plied only to the excrements of animals, either alone or mixed with straw, is now more widely used, and is given to all substances, or mixtures of substances, which are added to the soil in order to increase its productiveness or to restore the natural fertility lost by repeated cropping.

The subject of manures and their application involves a prior consideration of plant life and its requirements. The plant, growing as it does in the soil, and surrounded by the atmosphere, derives from these two sources its nourishment and means of growth through the various stages of its development. From these sources, each equally indispensable, the plant obtains the materials which it has the power of elaborating and building up to form its own structure.

Chemical analysis has shown that plants are composed of water, organic or combustible matters, and inorganic, incombustible, or mineral matters. These last are left as the ash when the plant is burnt. The elements forming the organic portion of plants are carbon, hydrogen, oxygen, and nitrogen; the mineral portion, or ash, consists prin-cipally of lime, magnesia, potash, soda, oxide of iron, phosphoric acid, sulphuric acid, chlorine, and silica.
The atmosphere is the great storehouse of organic plant-food. The carbonic acid always present in the air is, as is well known, eagerly taken up by the leaves of plauts, all of which have the power of decomposing carbonic acid, giving off its oxygen, and assimilating its carbon. Roughly speaking, three-fourths of the dry substance of all plauts is derived from the atmosphere.

Under conditions of natural growth and decay, when no crops are gathered in, or consumed on the laud by live stock, the herbage on dying down and decaying returns to the atmosphere and the soil the elements taken from them during life; but under cultivation a succession of crops deprives the land of the constituents which are essential to healthy and luxuriant growth. AYithout an adequate return to the laud of the matters removed in the produce, its fertility cannot be maintained for many years. In newly-opened countries, where old forests have been cleared and the land brought into cultivation, the virgin soil often possesses at first a high degree of fertility, but gradually its productive power decreases from year to year. Gene-rally speaking, it is more convenient to. clear fresh forest land than to improve more or less exhausted virgin land by the application of manure, labour, and skill. In all densely peopled countries where such a mode of cultiva-tion cannot be followed it is necessary to resort to arti-ficial means to restore the natural fertility of the land and maintain and increase its productiveness.

The researches of Liebig, Wiegmann, Polstorff, and others have proved beyond doubt the important functions of the mineral constituents of the soil in relation to plant life. The gradual removal of phosphate of lime in the tillage of dairy districts, or the removal of other mineral matters essential to the healthy growth of farm crops, certainly impoverishes the land. The exhaustion of the soil is caused in a much more marked way, however, by the rapid loss in available nitrogenous plant food which coils sustain when under cultivation without manure.
Agricultural improvements manifest themselves in two different directions—the mechanical and the chemical. Under mechanical improvement the physical condition of the soil is bettered aud its latent stores of plant food'brought into action by mechanical means, such as ploughing, sub-soiling, steam cultivation, &c. The introduction of new and superior agricultural implements, good systems of drainage, and intelligent division of labour characterize the first stage of progress in agriculture. The second stage is marked by the application of chemical principles to practical agriculture, an application shown by the intro-duction of a rational system of feeding, a proper rotation of crops, and chiefly the use of chemical, or artificial, manures for the purpose of restoring the natural fertility of the soil and increasing its productive powers.

The aid which chemistry has rendered during the last twenty-five or thirty years to practical agriculture has greatly promoted agricultural improvements ; and farming, which is in a large measure dependent for success upon an economical use of manures, is now being carried on much more rationally than in former times. The proper appli-cation of various kinds of manures is one of the most prominent features of successful modern farming.
In considering the economical use of manures on the land, regard must be had to the following points :—(1) the requirements of the crops intended to be cultivated; (2) the physical condition of the soil; (3) the composition of the soil; and (4) the composition of the manure. Briefly stated, the guiding principle of manuring economically and profitably is to meet the requirements of the crops intended to be cultivated, by incorporating with the soil, in the most efficacious states of combination, the materials in which it is deficient, or which the various crops usually grown on the farm do not find in the land in a sufficiently avail-able condition to ensure an abundant harvest.

Soils vary greatly in composition, and hence it will be readily understood that in one locality or on one particular field a certain manure may be used with great benefit, while in another field the same manure has little or no effect upon the produce. Although increased attention has of recent years been paid to the chemical composition and properties of soils, there is still much room left for improve-ment, for many farmers disregard almost altogether the composition of their fields in buying artificial manures.

It has been pointed out by Sir John Lawes that in actual English farm-practice there is, speaking practically, a standard of natural produce which varies within certain limits, as influenced by seasons and management, and which cannot be permanently increased or reduced by cultivation ; and further, when land is spoken of as being in " good condition," reference is made only to the tem-porary rise of fertility by means of the manures employed, while by land " out of condition " is signified the exhaus-tion of the manures by the removal of crops, loss by drain-age, etc., and that the soil has merely gone back to its standard of natural productiveness. Some soils, indeed, contain in their natural condition hardly a sufficient pro-portion of available elements of plant food to yield remunerative crops; such soils are naturally barren, and, although by the constant use of manures they may be improved and may attain some degree of fertility, they will, if left unmanured, speedily revert to their former natural unproductive state.

The principal constituents of manures are—nitrogen, in the form of ammonia, nitrates, and nitrogenous organic matters; organic matters not containing nitrogen (humus); phosphoric acid, potash, soda, lime, magnesia, silica, sulphuric acid, and chlorine. Of these constituents by far the most important are the nitrogen, phosphoric acid, aud potash, and these will be considered more in detail.

1. Nitrogen.—Nothing so much affects the productive-ness of soils as nitrogen, when it is supplied to plants in a form in which it can be assimilated by them, and nothing is more readily removed from the land, either in the crop grown or, in the form of nitrates, by drainage. The " good condition " of land, to which allusion has been made already, is, in a great measure, the fertility which has been imparted to the soil by the nitrogen supplied to it, while the " natural productiveness " may be taken as that due to the phos-phoric acid, potash, and other mineral constituents of the soil.

Supply of Nitrogenous Plant Food.—In the case of a crop growing under natural conditions, and not removed from the land, the mineral constituents taken from the soil, and carbonaceous as well as some nitrogenous organic matter, principally derived from the atmosphere, are returned to the land, and a rich carbonaceous soil or humus is produced in the course of years. Such a soil is capable of supplying for a considerable number of years, when under cultivation, the nitrogen needed by the crops grown on the land. This supply of nitrogen, however, gradually becomes exhausted by repeated cropping. The atmosphere, in addition to free nitrogen gas, which consti-tutes about four-fifths of its volume, contains but very little combined nitrogen in the forms of ammonia or nitric acid. M. Boussingault's experiments clearly show that plants do not possess the power of taking up iby their leaves and of assimilating the free nitrogen of the air. This conclusion has been verified by the extensive researches of Messrs Lawes, Gilbert, and Pugh. The nitrogen contained as nitric acid and ammonia in the air, and descending upon the land in the shape of rain, dew, or snow, though, without doubt, adding to the supply of nitrogen in the soil, is altogether insufficient to meet the requirements of re-munerative crops. The experiments of Messrs Lawes and Gilbert and Professor Way show that the average proportion of nitrogen deposited annually upon one acre of land at Rothamsted, St Albans, amounts to 7-21 ffi>. of which quan-tity 646 fb occur as ammonia and -75 ib as nitric acid.

The further investigations of Dr Voelcker, Professor Frankland, and Messrs Lawes and Gilbert upon the drainage water from cultivated soils show that a consider-able quantity of nitrogen in the shape of nitric acid passes into land drainage, and that this loss of nitrogen is much greater than the total amount supplied to the land by the rain and dew. The results which Messrs Lawes and Gilbert obtained in their experiments on the continuous, growth of barley at Rothamsted from 1852 to 1875 afford, as is shown in the following table (I.), direct evidence of the insufficiency of the atmospheric supply of nitrogen, and of that present in the soil in the form of nitrogenous organic matter.

TABLE I.-- Messrs Lawes and Gilbert's Experiments on the Growth of Wheat and Barley, year after year on the same Land, without Manure, and with different kinds of Manure.
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The Rothamsted soil is a moderately stiff one, of con-siderable depth, and contains naturally the mineral elements of plant food in abundance ; thus it has been possible to grow corn crops for over twenty-five years without any manure (Plots 1). The crops in the second period of twelve years were, however, less than those of the first period, and in neither case were full crops obtained. While the application of mineral manures alone (Plots 2) produced only a slight increase in the case of the wheat, and rather better, though poor, results with barley, nitrogenous manures, applied to the land either in the shape of ammonia salts or nitrate of soda, produced a strikingly large increase. The experiments further show that while good crops, both of wheat and barley, can be grown by the annual application of 14 tons of farmyard manure per acre, the best results are obtained by the use of a mix-ture of mineral and nitrogenous manures.

In Messrs Lawes and Gilbert's experiments the amount of nitrogen removed in different crops was determined with the following results:—over a period of thirty-two years (to 1875), wheat yieldedan averageof 20'7 Ibof nitrogen per acre per annum without any manure, but the annual yield has decreased from an average of over 25 lb in the first eight to less than 16 lb in the last twelve years, and since 1875 it has been still less; over a period of twenty-four years, barley, when unmanured, yielded an average of 18'3 B> nitrogen per acre per annum, but with a decline from 22 lb in the first twelve to 14-6 in the last twelve years. Experiments similar to those on wheat and barley have been made on oats, root crops, leguminous and grass crops, all showing the gradual decline in produce when grown continuously without nitrogenous manures, and prov-ing that the soil and not the atmosphere is the chief source of nitrogen in plants. In face of these results the "mineral theory" of Liebig, which attached but small value to nitrogen applied to the soil in the form of nitro-genous manures, aud maintained the sufficiency of the ammonia of the atmosphere for supplying the needs of the plant, cannot be accepted without reserve.

Notwithstanding the great effect produced by the nitrogenous manures, two-thirds of the nitrogen supplied vías unrecovered in the increase of crops when the ammonia salts were supplied to wheat in autumn. When, however, nitrate of soda was used, which is always applied in the spring, the quantity left unrecovered was not much more than half that supplied.

The following table (II.), by Messrs Lawes and Gilbert, shows the amount of nitrogen recovered, and the amount not recovered, in the increase of the crop for 100 supplied in manure, to wheat and to barley respectively, the result being in each case the average over a period of twenty years:—

TABLE II.
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The question will naturally be raised, What becomes of the one-half or two-thirds of the nitrogen which is not recovered in the increase of the crops 1 The examination of some seventy samples by Dr Voelcker, and a number of independent determinations by Dr Frankland, of the drainage-water from the experimental wheat plots which yielded the above results throw much light on this loss. The following table (III.) contains a summary of some of the more important results obtained.

TABLE III. -- Nitrogen as Nitrates and Nitrites, per 100,000 parts of Drainage Water from Plots Differently Manured, in the Experimental Wheat-field at Rothamsted, Wheat every year, commencing 1844.
== TABLE ==

These experiments show how great may be the loss of nitrogen by drainage when ammonia salts or nitrates are liberally applied to the land in autumn, should there be much wet weather in winter, or even when applied in spring if there be much heavy rain ; also, that the quantity of nitrogen in drainage water as nitrates is increased in proportion to the amounts of ammonia or nitrate employed on the land. Assuming that from one-quarter to nearly one-half the annual rainfall descends more than 40 inches below the surface, every inch of rain passing through the drains and carrying with it one part of nitrogen in 100,000 of water, there will be a loss of 1\ lb of nitrogen per acre from the manure. Dr Voelcker's analysis of the drainage water of a wheat field manured in autumn by ammonia salts supplying 82 lb of nitrogen per acre shows that for every inch of rain passing through the drains in January a loss took place of about 8J- lb of nitrogen, costing about Is. per lb as manure. The loss of nitrogen thus is very large, and shows that by far the largest proportion of the nitrogen of manure which is not recovered in the crop is lost in drainage. In addition to the nitrogen removed in the crop and to that lost in drainage, some small proportion is found by analysis to be retained in the soil itself. The nitrogen may be of advantage to crops grown subsequently, according to the source from which it was derived; for while ammonia salts and nitrates yield but very small residues, and exert little or no effect beyond the first year, from bones, cake, and other such materials we get large residues of nitrogen in the soil, which tell markedly on future crops. The experiments on drainage water have further shown the absorbent power of soils, and that manuring matters when in contact with soils undergo remarkable changes, being taken up by plants, not in the simple state in which they are applied, but in quite different kinds of combination. Professor Way has the merit of having first proved that all soils possess, in different degrees, the power of absorbing ammonia from its solution in water, and that in passing solutions of salts of ammonia through soils the ammonia alone is absorbed, and the acids of the ammonia salts pass through in combination, generally with lime, or, if lime be deficient, with magnesia or other mineral bases of the soil.





In the drainage investigations at Rothamsted, it was found that, although large quantities of ammonia salts were applied to some of the plots, the drainage water from them contained mere traces of ammonia, but at all times of the year nitrates were present in quantity; from this it would appear that it is chiefly, if not solely, from nitrates that crops build up their nitrogenous organic constituents. Before leaving the subject of drainage water it is worthy of note here that phosphoric acid and potash, the most valuable mineral fertilizing constituents of the manures, passed but little into the drainage water, but were retained almost entirely in the land, while the more abundant and less important mineral matters, such as lime, magnesia, soda, chlorine, sulphuric acid, and soluble silica, passed in large quantities into the drainage water. It follows from these investigations, first, that much more nitrogenous material must be applied to the land than would be needed to produce a given increase in the crop, supposing all the nitrogen to be recoverable ; and secondly, that nitrogenous organic matters when applied to the land undergo decom-position, and are gradually resolved into ammonia com-pounds, which, after being retained a short time by the soil, are finally oxidized into nitrates, in which form they are most available and beneficial to plants, but are not absorbed by the soil, and are readily washed out by rain. Nitrogen has great forcing properties, and is most beneficial when applied to crops in their early stages. Grass land on which nitrate of soda has been put as a top dressing shows very rapidly and markedly the effects of the manure.

Nitrate of soda, unless applied just at the time the crop is ready to take it up, will be largely wasted in drainage ; hence it is usual to apply nitrate of soda as a top dressing in spring. Ammoniacal manures, such as Peruvian guano, soot, sulphate of ammonia, <fcc., when used for winter wheat, are best applied in autumn, either before the wheat is sown or when it is fairly above ground. On light land they are often used as top dressings for wheat early in spring. The gradual decomposition of farmyard manures gives a more constant supply of nitrogen than the manures already noticed, and as the fermentation of clung proceeds but slowly it is best to apply it, when quite fresh, in autumn or winter, allowing it to decompose in the land and to yield nitrogen as nitrates when required in spring by the fresh growth of vegetation. In the case of nitrogenous organic materials, such as wool or hair refuse, which take even longer than farmyard manure to decompose, it is necessary to apply them some three or four months before the seed is sown.

2. Phosphoric Acid.—Next in value to nitrogen as a constituent of manures comes phosphoric acid. Of all the mineral or ash constituents of plants, this is the most im-portant, for the simple reason that it occurs in most soils in comparatively small proportions, and is required alike by corn and forage crops in larger quantities than lime, magnesia, and other mineral matters, which occur in most soils in almost inexhaustible quantities, or which, if defi-cient, can be easily and cheaply incorporated with the land.

Phosphoric acid occurs in soils principally in combination with lime as phosphate of lime, a constituent which enters largely into the composition of recent and fossil bones, coprolites, and guano, and of a variety of phosphatic minerals, such as Norwegian and Canadian apatite, Sombrero and Curacoa rock phosphate, South Carolina phosphate, Spanish and Portuguese phosphorite, &c. These and other phosphatic materials are now used largely in the manufacture of superphosphate aud other artificial manures.

Phosphate of lime is so sparingly soluble in pure water that, for all practical purposes, it may be considered to be insoluble in water; it is, however, attacked by the natural agencies at work iu the soil, and rendered available as plant food. According to the more or less porous condition of the phosphatic manuring materials, phosphate of lime is rendered more or less readily assimilable. Thus, while bone dust and guano, on account of their porous condi-tion, may be used with good effect as suppliers of phosphoric acid to the soil, others, such as hard and crystalline Canadian or Norwegian apatite, produce but little or no result when used as manures merely in a powdered state. It was in 1840 that Liebig suggested the treatment of bones with sulphuric acid in order to make their action more rapid. This treatment of bones by acid converts the phosphate of lime into a soluble lime salt called superphosphate, or, speaking chemically, trans-forms the original tribasic phosphate of lime into the mono-calcic phosphate, sulphate of lime being at the same time produced. Following on this, Mr (now Sir) John Lawes treated mineral phosphates similarly with sulphuric acid, and with results which led to the establishment of a new industry, the manufacture of superphosphate aud other artificial manures. The yearly importation of phosphatic minerals, <fec, into England for this manufacture alone exceeds 500,000 tons.

The acid or soluble phosphate of lime in superphosphate, when applied to the soil, is first dissolved by the rain, and equally distributed in a portion of the soil, in which it must be precipitated and rendered insoluble before it can be assimilated by the plant. It is this intimate distribu-tion aud subsequent precipitation in a most finely divided state that would seem to constitute the beneficial effects of superphosphate, and its superiority over undissolved phosphates. It supplies at once phosphoric acid, lime, and sulphuric achi to the soil, and is much used iu con-junction with nitrogenous materials. Superphosphates are manufactured of various strengths, the percentage of tribasic phosphate of lime, rendered soluble by acid, being taken as the basis of valuation.

3. Potash.—The next to rank after phosphoric acid as a valuable constituent of manures is potash. It enters largely into the composition of all crops, especially root crops. Sandy soils, as a rule, are poor in potash, for which reason they are benefited to a greater extent by the application of potash salts than most clay soils, which con-tain sufficient potash to meet the requirements of farm crops. In clay soils potash mainly occurs in the form of insoluble silicate of potash together with other silicates. By autumn cultivation, subsoiling, and similar means of facilitating the free access of the air to clay-land potash is gradually liberated from the insoluble silicates and is rendered available as plant food. Lime also seems to be an important agent in the liberation of potash. Potash also occurs in farmyard manure, urine, all excrements, in oil cakes, and largely in wood ashes.

Most potash salts are very soluble in water ; this explains their greater abundance iu the liquid than the solid excre-ments of animals. On this account it is a matter of importance, in making farmyard manure, to preserve the urine, and not lose the benefit of the potash salts it con-tains. On most soils in a good agricultural condition the addition of potash manures produces little or no effect, but on poor sandy soils or worn-out pasture land the use of potash salts, iu conjunction with superphosphate, dis-solved bones, and guano, is followed by most beneficial results. Potash salts as an addition to manures for potatoes have been found advantageous, while their effect on pasture seems to be to improve the quality of the herbage rather than to increase the yield of grass per acre.

4. Soda. —Most soils contain in abundance all the soda that farm crops require. With the exception of chloride of sodium (common salt), which occasionally is applied with more or less benefit to light sandy soils, and of nitrate of soda, which is employed as a nitro-genous manure, soda salts are not used for manuring purposes.

5. Lime.—Lime is essential for the production of healthy crops. Experience has shown that, when a soil is deficient in lime, farm-yard manure, Peruvian guano, and other manures, though used in abundance, produce comparatively but little effect. Again, on poor sandy soils, lime, marl, or chalk not unfrcquently produces better crops than farmyard or expensive artificial manures. Lime not only supplies an essential constituent of plants, but also prevents the loss by drainage of fertilizing matters such as potash, ammonia, and phosphoric acid. One of the functions of lime in the soil is to combine with the acids of the potash and ammoniacal salts of guano and of farmyard and other manures, and to liberate potash and ammonia, which are retained in the land, while the inexpensive lime salts pass into the land drainage.

Lime is used in agriculture in the form of quicklime, chalk (carbonate of lime), gypsum (sulphate of lime), marl, and shell-sand. For liming purposes gas-lime also is frequently employed, and, if well exposed to the air before being put on the land, may be used with safety and advantage.

6. Magnesia. —Magnesia is of but slight importance in manures ; it occurs with potash in kainite and other potash sails, and the sulphate is sometimes used in making up artificial manures, but apparently without benefit.

7. Silica.—Silica is a constituent of the ashes of all plants, and occurs specially in large proportion in the straw of cereal crops. All soils contain such an abundance of silica that no necessity exists of supplying it artificially.

8. Chlorine, Sulphuric Acid, and Oxide of Iron.—These ash constituents are of little practical importance, inasmuch as most soils contain a sufficiency of them to meet the requirements of the crops usually cultivated on the farm. It may be observed, how-ever, that chlorine has been found to be essential to plant life, and that iron is necessary for imparting to plants their green colour.

9. Organic Matter or Humus. —The i mportance of organic matter in manures was formerly much exaggerated. It has been con-clusively proved that the carbon of which the bulk of the dry sub-stance of all agricultural produce consists is derived from the carbonic acid of the atmosphere, and not from humus of the soil or the non-nitrogenous organic matters supplied in the manure. The organic matters present in dung iu the shape of more or less decomposed or rotten straw exert a beneficial effect by improving the physical condition of both light and heavy laud.

TABLE IV. — The Composition of Farmyard Rotted Dung from Horses, Cows, and Pigs, in 100 Parts.

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Farmyard Manure.-—Farmyard manure is composed of the urine and solid excrements of animals collected in the stalls or yards, together with the straw used as litter. Its composition varies greatly, according to the quantity of straw used as an absorbent, the nature of the animals, the food they have consumed to produce it, the length of time and way in which it has been kept, &c. The analysis by Dr Voelcker of well-made farmyard manure from horses, cows, and pigs, given in Table IV., p. 509, will show its approximate composition.

This analysis shows that farmyard manure contains all the constituents, without exception, which are required by cultivated crops to bring them to perfection, and hence it may be called a perfect manure. Dung, it will be observed, contains a great variety of organic and inorganic compounds of various degrees of solubility, and this complexity of composition—difficult, if not impossible, to imitate by art —is one of the reasons which render farmyard manure a perfect as well as a universal manure.

The excrements of different kinds of animals vary in composition, and those of the same animal will vary according to the nature and quantity of the food given, the age of the animal, and the way it is generally treated. Thus a young animal which is growing needs food to produce bone and muscle, and voids poorer dung than one which is fully grown and only has to keep up its condition. The solid and liquid excrements differ much in composition, for, while the former contains a good deal of phosphoric acid, lime, magnesia, and silica, and comparatively little nitrogen, the urine is almost destitute of phosphoric acid, and abounds in alkaliue salts and nitrogenous organic matters, which on decomposition yield ammonia. Unless, therefore, the two kinds of excrements are mixed, a perfect manure supplying all the needs of the plant is not obtained; care must accordingly be taken to absorb all the urine by the litter. Farmyard manure, it is well kuown, is much affected by the length of time and the way in which it has been kept. Fresh dung is soluble in water only to a limited extent, and in consequence it acts more slowly on vegeta-tion, and the action lasts longer than when dung is used which has been kept some time; fresh dung is therefore gene-rally used in autumn or winter, and thoroughly rotten dung in spring, when an immediate forcing effect is required.





The changes which farmyard manure undergoes on keep-ing are illustrated by the following table of analyses, by Professor Wolff of Hohenheim in Würtemberg, of farm-yard manure in its different stages of decomposition :—

TABLE V.—Average Percentage Composition of Farmyard Manure.

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These figures represent the composition of farmyard manure of rather poor quality. Well-made good dung, produced by fattening cattle fed upon a fair allowance of cake, roots, hay, and straw, on an _ average may be said to contain—
Potash .......... 0.50 per cent.
Phosphoric acid .......... 0.53 per cent
Nitrogen .......... 0.64 per cent

Forty tons of dung, according to this estimate, contain in round numbers 448 lb of potash, 475 of phosphoric acid, and 573 of nitrogen.

During the fermentation of dung a large proportion of the non-nitrogenous organic matters disappears in the form of carbonic acid and water, while another portion is con-verted into humic acids which effectually fix the ammonia gradually produced from the nitrogenous constituents of the solid and liquid excrements. The mineral matters remain behind entirely in the rotten dung, if care be taken to prevent loss by drainage.

Well-fermented dung, it will be noticed from the preced-ing table, is more concentrated and consequently more efficacious than fresh farmyard manure. Neither fresh nor rotten dung contains any appreciable quantity of volatile ammonia, and hence there is no necessity for applying gypsum, dilute acid, green vitriol, or other sub-stances recommended as fixers of ammonia. If dung is carted out into the field and spread out at once it may be left for weeks together before it is ploughed in without the slightest risk of sustaining loss in fertilizing matter by evaporation, for dung dues not lose ammonia by evapora-tion on exposure to the air, and any mineral soluble salts will be washed into the soil where they are wanted. If, however, dung is kept for a length of time in shallow heaps, or in open straw-yards and exposed to rain, it loses by drainage a considerable proportion of its most valuable soluble fertilizing constituents.

With a view to ascertaining the loss in fertilizing sub-stances which farmyard manure sustains when it is kept for a long time exposed in open yards to the deteriorating influences of rain, Dr Voelcker spread a weighed quantity of fresh dung of known composition in an open yard, and after a period of twelve months again weighed the dung and submitted it to analysis, when the results shown in Table VI. were obtained :—
After 12 Months' Exposure. 793-65 622-SO 170-85
Fresh Manure.
1652 1003 559

TABLE VI.—Showing the Loss which Dung sustains by Drainage in Open Yards.
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These tabulated results showed that the manure lost 69-8 per cent, of its fertilizing matters; or, in round numbers, two-thirds of the dung was wasted and only one-third left behind. Thus, after twelve months' exposure to the weather, nearly all the soluble nitrogen and 78-2 per cent, of the soluble mineral matters were lost by drainage. To prevent this loss, farmyard manure, as had been already pointed out, should, when possible, be carted into the field, spread out at once, and ploughed in at the convenience of the farmer. It is, however, not always practicable to apply farmyard manure just at the time it is made, and, as the manure heap cannot be altogether dispensed with, it is necessary to see how the manure may best be kept. For proper decomposition both air and moisture are requisite, while extreme dryness or too much water will arrest it. Farmyard manure is either prepared in dung-pits, which are put in a separate place, or is accumulated under the animal in the feeding-boxes ; of the two plans the latter is the better, the urine being more thoroughly absorbed, and, owing to the box manure being more compact through constant treading on it, air enters less freely and the decomposition goes on less rapidly, the volatile matters in consequence, not being so readily lost. External agents, such as rain, wind, sun, &c, do not affect it as they would in the case of dung-pits. If farmyard manure must be stored in heaps, care should be taken to have the bottom and sides of the pit impermeable to water, and the bottom slightly inclined to allow any liquid manure which collects to run off into a tank below, from which, by means of a pump, it may be again poured over the heap. A concrete bottom for the pit is best, or, failing that, one of thick clay or well-beaten earth. The manure heap should be kept as compact as possible, aud always moist. The advantage of farmyard manure lies, not only in its supplying all the con-stituents of plant food, but also in the improved physical condition of the soil through its application, as the land is kept porous, and air is allowed free access. While, how-ever, farmyard manure has these advantages, experience has shown that artificial manures, properly selected to meet the requirements of the crops intended to bo grown, due regard being had to the chemical composition of the soil, may be employed to greater advantage. In farmyard manure about two-thirds of the weight is water and one-third dry matter; a large bulk thus contains only a small proportion of fertilizing substances, and expense is incurred for carriage of much useless matter when dung has to be carted to distant fields. When a plentiful supply of good farmyard manure can be produced on the farm or bought at a moderate price in the immediate neighbourhood, it is economy to use it either alone or in conjunction with artificial manures; but when food is dear and fattening doe3 not pay, or farmyard manure is expensive to buy, it will be found more economical to use artificial manures.

Manures from Feeding Stuffs.—The investigations of Messrs Lawes, Gilbert, and Mure have shown that, in estimating the value of animal manure, 90 per cent, of the nitrogen of the food may be reckoned to be recovered in the case of feeding cakes, pulse, and other highly nitrogenous feeding stuffs; 85 per cent, in the case of foods compara-tively poor in nitrogen, such as cereals and roots ; and less than 65 per cent, in the case of bulky feeding stuffs, such as hay and straw. As a source of manure, the value of fattening foods is greater the more nitrogen they contain. Practically speaking, the whole of the mineral constituents and about nine-tenths of the nitrogen of the food are recovered in the dung and urine. For the same weight of dry substance consumed, oxen void more manure than sheep, and sheep more than pigs. The composition of the different foods given to fattening animals being well known, it is easy to calculate the amounts of nitrogen, phosphoric acid, and potash of the food which will be recovered in the manure. Each constituent having its market value as a manuring constituent, the money value of the manure obtained from the consumption of a ton of any ordinary food of which the composition is known can be determined. Assuming ammonia to be worth 8d. per lb, potash 2d. per lb, and phosphate of lime Id. per lb, the money value of the manure produced by the consumption of a ton of various foods is given by Mr Lawes in the following table (VII.), which also shows the general composition of the different foods as far as their manurial value is concerned.

In these estimates it is presumed that the manure can be put on the land without loss, but in practice some loss is unavoidable; it may be but slight, as, for instance, when sheep are fed on the land, or when the manure is made in feeding-box°s, but it will be considerable when the food has been consumed in open yards in a very rainy season. Allowances must thus be made for the circumstances under which the manure was produced.

TABLE VII.—Composition of Ordinary Feeding Stuffs in 1000 parts, and their Manuring Value per Ton.
== TABLE ==

Artificial Manures.—By some a distinction has been drawn between those manures which, like superphosphate, dissolved bones, &c, are manufactured in chemical works and those which are produced naturally, such as guano, nitrate of soda, &c. However, the term artificial manure is generally applied to all manures, natural or manufactured, which are not produced on the farm, as distinguished from farmyard manure and manure from purchased foods, which are essentially farm products. The value of all manures mainly depends on their chemical composition.

As compared with farmyard manure, artificial manures have the disadvantage that they, unlike it, do not improve the physical condition of the soil. Artificial manures have, on the other hand, the advantage over farmyard manure that they can supply in a small compass, and even if used in small quantity, the needed nitrogen, phosphoric acid, and potash, &c, which crops require, and which farmyard manure has but in small proportion; they present the expensive fertilizing matters in a concentrated form, and by their application save expense in labour and carriage.

The following are the principal artificial manures in use :—

1. Nitrogenous Manures.—Peruvian Guano.—This is a natural manure, valuable on account of the ammonia, phosphoric acid, and potash it contains. It is the excrement, &c., of sea birds accumu-lated in parts where no rain falls. The earliest deposits found contained as much as 14 to 17 per cent, of ammonia, e.g., Chmchas Island guano; those now (1882) imported seldom exceed 8 per cent., and generally vary from 4 to 8 per cent., of ammonia. In using guano it should be mixed with earth, &o., to prevent injury to the seeds or plants. Peruvian guano is also treated with sulphuric acid, which renders the phosphates soluble and fixes the ammonia, thereby preventing any loss of it; this constitutes dissolved guano, and is frequently sold upon a guarantee of 20 per cent, of soluble phosphates, 4 per cent, of insoluble phosphates, and 9 per cent, of ammonia. Peruvian guano is used as a top dressing for wheat and barley ; in addition to insoluble phosphates, it contains soluble phosphates of the alkalies.

Ammonia Salts.—The principal one is sulphate of ammonia, largely produced in gas works by neutralizing gas liquor with sulphuric acid ; it is usually sold on a basis of 24 to 25 per cent, of ammonia.

Soot is valuable on account of the sulphate of ammonia it con-tains; the percentage of ammonia varies from 1J to 4.

Nitrate of soda is a natural deposit; it is greatly used as a top dressing for wheat and barley. It usually contains common salt, and when purified is sold on a basis of 95 per cent, of pure nitrate.

Organic Nitrogenous Substances.—Wool, hair, fish, flesh, horn, blood, rape cake, damaged cotton cake and other oil cakes. Wool refuse (shoddy), according to its quality, contains from 4 to 8 percent, of nitrogen, flesh 14 to 15 per cent., blood (dried) 13 to 15 per cent., rape cake 4 to 5 per cent., linseed cake about 4 per cent., cotton cake (undecorticated) nearly 4 per cent., and cotton cake (decorticated) over 6 per cent, of nitrogen.

2. Phosphatic Manures.—
(a) The following phosphatic minerals are used for the manufacture of superphosphate of various strengths, and of compound manures :—coprolites (Cambridge, Suffolk, and Bedfordshire), containing 50 to 55 per cent, of phosphate of lime ; phosphorite (Spanish and Portuguese); apatite (Norwegian and Canadian), containing often as much as 80 per cent, phosphate of lime ; South Carolina (land and river) phosphate, 52 to 56 per cent, phosphate of lime ; French phosphate ; Sombrero phosphate, 70 per cent, phosphate of lime ; Curagoa phosphate, 80 per cent, phosphate of lime ; Navassa phosphate ; Aruba phosphate, &c.

(b) Bones.—Raw bones, as J inch and jt inehbones; bonemeal; bone dust, having about 48 per cent, phosphate of lime and 4| per cent, of ammonia ; boiled bones, with 60 per cent, phosphate of lime and about 1 '8 per cent, of ammonia; dissolved bones ; bone ash, with 70 per cent, phosphate of lime ; animal charcoal, with 70 to 80 per cent, phosphate of lime.

(c) Phosphatic Guanos.—Lacepede Island guano; Mexillones guano ; Maiden Island guano; Fanning Island guano; and many others varying in composition from 60 to 90 per cent, phosphate of lime.

3. Saline Materials.—Potash salts (chloride and sulphate); kainite, with 20 to 25 per cent, sulphate of potash, and also sulphate of magnesia and common salt; wood ashes, with about 10 per cent, of potash; common salt.

4. Calcareous Manures.—Lime, chalk, marl, gypsum, shell sand, gas lime, coal ashes, road scrapings, &c.

5. Carbonaceous Manures.—Sawdust, peat, sea-weed, vegetable refuse, &c.

6. Special and Compound Manures.—The basis of these is super-phosphate, which is mixed with other manuring materials to meet the special requirements of particular crops and soils.

The foregoing remarks made on the application of manures to different kinds of crops may now in conclusion be summed up. Farmyard manure, in order to be most beneficial, should be applied as quickly as possible after it is made, the best time being in autumn or early winter. Nitrate of soda should be applied as a top dressing early in spring ; its effect will be seen in the first season only. Ammonia salts, guano, dung, &c, are best applied to heavy land in autumn or winter, either before the seed is sown, or after the plant is fairly above ground, but in the case of light land early in spring. The effect of bones in the various form of dissolved bones, bone dust, raw bones, &c, will last two or more seasons according to the quantities used and their respective solubility. Lastly, it may be observed that the presence of lime is essential to the economical use of manures.

As regards cereal crops, it has been found that mineral manures alone, whether simple or complex, do not pro-duce appreciable increase of crop, but that nitrogenous manures, whether as ammonia salts, nitrate of soda, or farmyard manure, greatly benefit the crop; that nitrate of soda doe3 rather better than ammonia salts; and that, while on fairly heavy land farmyard manure will yield good crops, the best results are obtained by using mineral and nitrogenous manures together. On clay soils a top dressing of nitrate of soda often answers all practical purposes, but on light soils nitrate of soda or ammonia salts should not be used without mineral manures, while it is advisable even on heavy land to use superphosphate as well.

For root crops, on cold clays nothing answers so well as mineral superphosphate alone, but on light land dissolved bones, bone dust, precipitated phosphate, or a compound artificial manure will be found to be much preferable to superphosphate. Bone meal mixed with mineral super-phosphate makes, for instance, a good manure for roots; for mangolds Peruvian guano and common salt in addition are useful, and for potatoes potash salts with phosphatic and nitrogenous manures.

For pasture land the use of artificial manures is, as a rule, not economical; nitrogenous manures raise the quantity and phosphatic and potash manures improve the quality of the herbage, while, for worn-out pastures, potash with dissolved bones or superphosphate or super-phosphate and guano will do much good. The most economical way of manuring pasture laud is to apply farm-yard manure liberally, or feed it off with cattle, giving cotton cake iu addition.

The employment of artificial manures in a judiciou manner has shown the occupier of laud that it is not necessary for him to be bound down to any system of rotation of crops which may be practised in his particular district, but that he has the means of pursuing the course of cropping, system of manuring, and general management of his farm which will yield him the best returns. No more striking instance of this could be put forward than the experience of Mr Prout, who at Sawbridgeworth, Herts, has grown with much success cereal crops, year after year, on heavy clay land, selling the whole of the growing crops, and restoring the fertility of the soil by artificial manures. The land was purchased in 1861, and up to the present time (1882) the crops have been as good as ever, and the land has not been deteriorated, but on the other hand improved, by continuous corn growing. The experiments of Messrs Lawes and Gilbert at liothamsted and of Dr Voelcker at Woburn have been thus verified on a large scale in the experience of Mr Prout, and have shown beyond all possibility of doubt the efficacy and economy of a liberal use of artificial manures. (A. V.)


Footnotes

507-1 Previous cropping :—1839, turnips with farmyard manure ; 1S40, barley; 1841, pease; 1842, wheat ; 1843, oats; the last four crops unmanured. First experimental wheat crop in 1844. Wheat every year since ; and, with some exceptions, nearly the same description of manure on the same plots each year—especially during the last twenty-six years (1852 and since). Unless otherwise stated, the manures are sown in the autumn before the seed. Area under ex-periment about 13 acres.

507-2 Previous cropping :—1847, Swedish turnips with dung and super-phosphate of lime, the roots carted off; 1848, barley ; 1849, clover ; 1850, wheat; 1851, barley manured with ammonia salts. First ex-perimental crop in 1352. B.niey every year since.


The above article was written by: A. Voelcker, F.R.S., Professor of Chemistry to the Royal Agricultural Society of England.



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