Application of Farmyard Manure to the Field.
In applying the manure to the field, and before ploughing it in, two methods of procedure may be pursued. First, the manure may be set out in heaps, larger or smaller, over the field, and be allowed to remain in these heaps some time before being spread; and secondly, it may be directly spread broadcast over the field, and thus allowed to lie for some time. Lastly, the manure may be ploughed in immediately; and it may be stated that such a method is, where circumstances permit, the safest and most economical method.[171]
In discussing the merits and demerits of these two methods, Dr Heiden points out, first, with regard to the distribution of the manure in small heaps over the field, that this is not to be recommended, on the following grounds:—
1. Because the chances of loss by volatilisation are thereby increased. The manure is distributed several times instead of only once or twice.
2. It is apt to ensure unequal distribution. The separate heaps run the risk of losing their soluble nitrogenous matter, which soaks into the ground beneath the heaps. The other portions of the field not covered by the manure-heaps are thus manured with washed-out farmyard manure, bereft of its most valuable constituents. The result is, that while certain portions of the field are too strongly manured, other portions are too weakly manured.
3. The proper fermentation of the manure is apt to be interfered with by the loss of that which is its most important agent—viz., the soluble nitrogenous matter—and also by the drying action of the wind.
The same objections hold good to a large extent with regard to the setting out in the fields of the manure in large heaps. The risks of loss, in one respect, may be said to be less, owing to the smaller surface presented. On the other hand, they may be greater, owing to fermentation taking place more quickly. Agricultural practice, however, often renders this custom necessary; and if precautions are taken not to let the heap lie too long, and to cover it over with earth, the risk of serious loss may be rendered inconsiderable.
With regard to the second method of procedure—viz., the spreading of the manure broadcast over the field, and allowing it thus to lie—Dr Heiden is of opinion that this should only be done when the field is level. In the case of uneven ground the risks are, of course, obvious. It has been affirmed that, by allowing farmyard manure thus to lie exposed for some time, an important loss of volatile ammonia—carbonate of ammonia—is apt to take place. This could only take place where the former treatment of the farmyard manure had been bad. Hellriegel has shown that in the case of properly prepared farmyard manure there is no danger of loss in this way. The absorptive power of the soil for ammonia, it must be remembered, is very great, and the amount of volatile ammonia in farmyard manure is relatively so small that it is scarcely possible that any could escape in this way. Hellriegel's experiments have demonstrated this in a very striking way. He has found that in the case of a chalky soil, and during the summer and autumn months, practically no loss of ammonia takes place. The following considerations may be further urged in support of this method of application, as against immediately ploughing in the manure, viz.:—
1. That fermentation takes place more quickly.
2. That it results in a more equable distribution of the manurial constituents in the dung, by gradually and thoroughly incorporating the liquid portion of the manure with the soil-particles.
Against, however, these undoubted advantages, one serious disadvantage may be urged—viz., that the manure, before being ploughed in, becomes robbed to a large extent of its soluble nitrogenous compounds, which, as we have repeatedly observed, are so necessary for fermentation; and that, therefore, when it is ploughed in, it does not so readily ferment. This being so, it is highly advisable, in the case of light or sandy soils, not to follow such a practice, but to plough the manure directly in.
As to the depth to which it is advisable to plough the manure in, it may be here noticed that it should not be too deep, so as to permit of the access of sufficient moisture to ensure proper fermentation, and to prevent rapid washing down of nitrates to the drains. Lastly, it need scarcely be pointed out that it is highly important to have the manure evenly and thoroughly incorporated with the soil-particles. Where the manure is permitted to cake together in lumps, it may successfully resist the action of fermentation for several years.
Value and Function of Farmyard Manure.
Practical experience has long demonstrated the fact that farmyard manure is, taking it all round, the most valuable, and admits of the most universal application, of all manures; and science has done much to explain the reason of this. The influence of farmyard manure is so many-sided that it is difficult even to enumerate its different functions. As has already been pointed out, its indirect value as a manure is probably as great as, if indeed even not greater than, its direct value. In concluding our study of farmyard manure, we shall endeavour to summarise, in as brief a manner as possible, its chief properties.
First, as to its value as a supplier of the necessary elements of plant-food. This, there can be little doubt, has been, and still is, grossly exaggerated by the ordinary farmer. Much has been claimed for it as a "general" manure. How far it merits pre-eminence on this score among other manures will be seen in the sequel. It is true that, since it is composed of vegetable matter, it contains all the necessary plant ingredients.[172] As has been shown in the Introduction, there is practically in the case of most soils no necessity to add to a manure any more than the three ingredients, nitrogen, phosphoric acid, and potash. Its value, then, as a direct manure, must depend on the quantity and proportion in which these three ingredients are present. These substances, as we have already seen, it contains only in very small quantities. It is, judged from this point of view, a comparatively poor manure. Furthermore, only a certain percentage of these substances is in a soluble or immediately available condition,—in this respect the rotten manure being very much more valuable than the fresh manure.
Again, a point of great importance in a universal manure is the proportion in which the necessary plant-foods are present. If it be asked, Are the nitrogen, phosphoric acid, and potash in farmyard manure present in the proportion in which crops require these constituents? the answer must be in the negative. Heiden[173] has very strikingly illustrated this point, in so far as the relations between the two ash ingredients are concerned, by some computations as to the amount which would be removed from the soil in the course of different rotations.[174] In the case of five different rotations it was found that the ratio between the potash and phosphoric acid removed was as follows:[175] (1) 2.96 to 1; (2) 2.76 to 1; (3) 2.95 to 1; (4) 4.13 to 1; (5) 3.78 to 1. This would give a mean of 3.32 to 1. This is not the ratio in which these ingredients are generally present in farmyard manure. Farmyard manure may be said to be much richer in the mineral constituents of plants than in nitrogen. Professor Heiden found that in the case of a farm at Waldau, the crops in the course of ten years removed from a morgen (.631 of an acre) the following quantities:—
| lb. | |
| Nitrogen | 329 |
| Potash | 263 |
| Phosphoric acid | 121 |
In order to supply these amounts the following quantities of manure would require to be supplied:—
1. For the nitrogen, 26 or 27 tons (manure containing .606 per cent nitrogen).
2. For the potash, 20 to 25 tons (manure containing .672 per cent potash).
3. For the phosphoric acid, 13 to 19 tons (manure containing .315 per cent phosphoric acid).
From the above it will be seen that farmyard manure contains too little nitrogen in proportion to its ash ingredients.
It is not merely the amount of fertilising ingredients removed by the crop we have to take into account in estimating the value of certain manurial ingredients for the different crops. Two other considerations have to be remembered—viz., the amount of the constituents already present in the soil, and the ability of the different crops to obtain the ingredients from the soil. If we take into account these two considerations in estimating the value of farmyard manure as a general manure, we shall find that they accentuate the inadequacy of the ratio existing between the nitrogen and the mineral ingredients. Messrs Lawes and Gilbert have found in the Rothamsted experiments with farmyard manure, that while it restored the mineral ingredients, it was inadequate as a sufficient source of nitrogen. Nitrogen is, of all manurial ingredients, in least abundance in soils. It is consequently found that the ingredient in which farmyard manure requires to be reinforced is nitrogen. With regard to phosphoric acid and potash, it has already been shown that the ratio between them is probably greater than that in a good average manure. We should, arguing from this alone, be inclined to think that farmyard manure would be best reinforced with potash. The reverse is the case, however, as every farmer knows. This is due, first, to the fact that the potash, unlike the phosphoric acid, is entirely of a soluble nature, and therefore immediately available for the plant's needs; and secondly, to the fact that the necessity for the application of potash as a manure is generally not nearly so great as in the case of phosphoric acid. The result is, that farmyard manure will be, as a rule, more valuably supplemented by phosphoric acid than by potash.
Another point of great importance, in estimating the value of farmyard manure as a chemical manure, is the inferior value possessed by much of the nitrogen it contains, as compared with the nitrogen in such artificial manures as nitrate of soda and sulphate of ammonia. According to the Rothamsted experiments, weight for weight, the nitrogen in farmyard manure is not half so valuable as it is in sulphate of ammonia. Much of the nitrogen becomes only very slowly available; not a little of it perhaps actually takes years to be converted into nitrates.[176]
Thus, with regard to the direct value of farmyard manure as a manure, we have seen—
1. That it contains a very small quantity of the three fertilising ingredients.
2. That the proportion in which these three ingredients are present is not the best proportion for the requirements of crops.
3. That the form in which a portion of these ingredients—nitrogen and phosphoric acid—is present is not of the most valuable kind.
It is consequently not as a direct chemical manure that farmyard manure is pre-eminently valuable. We must seek for perhaps its most valuable properties in its indirect influence.
It adds to the soil a large quantity of organic matter. Most soils are improved by the addition of humus. The water-absorbing and retaining powers of a soil are increased by this addition of humus, while it enables the soil to attract an increased amount of moisture from the air. This is often of great importance, as in the period of germination of seed.[177] The influence it exerts on the texture of the soil in the process of fermentation is also very great. This is especially so in soils whose texture is too close, such as heavy clayey soils. It opens up their pores to the air, and renders them more friable. Where such an influence is most required, as in clayey soils, the manure ought to be applied in a fresh condition, so that the maximum influence exerted by the manure in this direction may be experienced. On light soils, on the contrary, whose friability and openness are already too great, and which do not require to be increased, the manure will be best applied in a rotten condition. It adds, further, greatly to the heat of the soils by its decomposition. Thus on cold damp soils it effects one very marked benefit. The influence it exerts in its decomposition upon the fertilising ingredients present in the soil is also by no means inconsiderable. In the process of its fermentation large quantities of carbonic acid gas are generated. This carbonic acid probably acts in a double capacity. It will, in the first place, greatly increase the solvent power of the soil-water, and thus enable it to set free an increased amount of mineral plant-food; and secondly, it will help to conserve a certain quantity of the soil-nitrogen, by preventing its conversion into nitrates.
As its indirect and mechanical properties are greatest when in its fresh condition, it will be better to apply it in that condition to soils most lacking in these mechanical properties. We may therefore say that farmyard manure is best applied in a rotted condition to light sandy soils, and to soils in a high state of cultivation, where its mechanical properties are not so much required.
An important point still remains to be discussed—viz., the rate at which the farmyard manure should be applied. This, of course, should naturally depend on a variety of circumstances—the amount of artificial manures used as supplementary to the farmyard manure, the frequency of its application, and the nature of the soil.
These considerations naturally vary so much, that the quantities of farmyard manure it is advisable to apply in different cases are widely different. There is a strong probability that the rate at which farmyard manure has been applied in the past has been grossly in excess of what could be profitably employed. Opinion is gaining ground among practical farmers, that smaller and more frequent applications of farmyard manure to the soil would be fraught with better results than the older custom of applying a large dressing at a time. This is an opinion in the support of which science can urge strong arguments. It is only of late years that we have come to recognise sufficiently the various risks which all fertilisers are subject to in the soil, and the importance, therefore, of minimising these risks as much as possible by putting into the soil at one time only as much manure as it is safely able to retain.
"The famous old German writer Thaer regarded 17 or 18 tons as an abundant dressing; 14 tons he called good, and 8 or 9 tons light. Other German authorities speak of 7 to 10 tons as light, 12 to 18 tons as usual, 20 or more tons as heavy, and 30 tons as a very heavy application."[178]
In the new edition of Stephens' 'Book of the Farm,'[179] from 8 to 12 tons per acre for roots, and from 15 to 20 tons for potatoes, along with artificials, which may cost from 25s. to 60s. per acre additional, are quoted as general dressings.
The majority of recent experiments with farmyard manure would seem to indicate that, even in the case of what are considered small dressings, the extra return in crop the first year after application is not such as to cover the expense of the manure. Of course, as is commonly pointed out, the effect of farmyard manure is of a lasting nature, and is probably felt throughout the whole rotation, or even longer. This, to a certain extent, is no doubt true; still it may be strongly doubted whether farmyard manure is, after all, an economical manure, as compared with artificial manures. The desirability of manuring the soil and not the crop is, in this age of keen competition, no longer believed in; and the Rothamsted experiments have shown that it is highly doubtful whether even the soil benefits to anything like a commensurate extent by the application of large quantities of farmyard manure. This is of course assuming for farmyard manure the value that it would fetch when sold, or, to put it rather differently, the price it would cost if the farmer had to purchase it. Farmyard manure is a necessary bye-product of the farm, and can scarcely be regarded, therefore, in the same light as the artificial manures which the farmer buys.[180]
FOOTNOTES:
[131] See Appendix, Note I., p. 279.
[132] "The large amount of potash in unwashed wool is very remarkable: a fleece must sometimes contain more potash than the whole body of the shorn sheep."—Warington's 'Chemistry of the Farm,' p. 78.
[133] See Appendix, Note II., p. 279.
[134] The urine of the pig, from the nature of its food, is, as a general rule, a very poor nitrogenous manure.
[135] See Appendix, Note XV., p. 290.
[136] See Appendix, Note III., p. 280.
[137] See Appendix, Note XVIII., p. 291.
[138] The nitrogen present in the urine, it may be well to point out, is derived from the waste of nitrogenous tissue as well as from nitrogenous matter of the food digested.
[139] Note IV., p. 281.
[140] Warington puts this matter admirably in the following words: "If the food is nitrogenous and easily digested, the nitrogen in the urine will greatly preponderate. If, on the other hand, the food is one imperfectly digested, the nitrogen in the solid excrement may form the larger quantity. When poor hay is given to horses, the nitrogen in the solid excrement will exceed that contained in the urine. On the other hand, corn, cake, and roots yield a large excess of nitrogen in the urine." ('Chemistry of the Farm,' p. 137).
[141] See p. 281.
[142] See p. 282.
[143] See Heiden's 'Düngerlehre,' vol. ii. p. 58.
[144] Heiden's 'Düngerlehre,' vol. i. p. 404.
[145] The following quantities of nitrogen are found in rye, pea, and bean straw:—
| Ranging from | Average | Lb. | |
| per cent. | per cent. | per ton. | |
| Rye-straw | .30 to .73 | .57 | 12.76 |
| Pea-straw | .76 to 1.61 | 1.21 | 27.10 |
| Bean-straw | 1.15 to 2.62 | 1.92 | 43.00 |
[146] Dr J. M. H. Munro recommends the sprinkling of a little finely sifted peat-powder in addition to straw, as an excellent means of preventing loss of volatile ammonia in the fermentation of manure.
[147] See 'Mark Lane Express,' October 7, 1889, p. 475.
[148] See Appendix, Note VII., p. 283.
[149] For analyses see Appendix, Note VIII., p. 283.
[150] According to Storer, in a ton of autumn leaves of the best quality there would be 6 lb. of potash, less than 3 lb. of phosphoric acid, and 10 or 15 lb. of nitrogen. Another substance that may be used as a litter is sawdust. This substance is a good absorbent, but is of little value as a manurial substance.
[151] Heiden's 'Düngerlehre,' vol. ii. pp. 34, 66. In Boussingault's experiments the food consisted of 15 lb. hay, 4.54 lb. oats, and 32 lb. water; the total excrements amounting to 31.16 lb., containing 7.42 lb. dry matter. In Hofmeister's experiments the food consisted of 5.23 lb. hay, 6.18 lb. oats, 1 lb. chopped straw, and 25.57 lb. water; the excrements amounting to 25.07 lb., containing 5.32 lb. dry matter.
[152] This is taking no account of the amount of water which the manure will absorb, and which will probably double the quantity.
[153] See Appendix, Note IX., p. 283.
[154] The rapid fermentation of horse-manure is due to its mechanical as well as its chemical nature. The horse does not reduce its food to such small pieces, and its urine is rich in nitrogen.
[155] Schulze recommends one-third of a pound per day of sulphate of lime for each horse.
[156] See Appendix, Note X., p. 284.
[157] The food consisted of 30 lb. potatoes, 15 lb. hay, and 120 lb. water.
[158] For further analyses of cow-manure, see Appendix, Note XI., p. 286.
[159] This is for a pig of six to eight months old, and fed on potatoes.
[160] It has been asserted that the use of pig-manure, when applied alone, is apt to give an unpleasant taste to the produce grown.
[161] Taken from a very large number of analyses by a number of experimenters. See Heiden's 'Düngerlehre,' vol. i. p. 99.
[162] See Storer, 'Agricultural Chemistry,' vol. ii. p. 96.
A question of great importance is as to the amount of farmyard manure produced on a farm in a year, and its value. This is a question which is extremely difficult to satisfactorily deal with. Various methods of calculating this amount have been resorted to. It may be well to state these pretty fully. Some practical authorities estimate the amount by calculating that every ton of straw should produce 4 tons of manure. Another method consists in estimating the amount from the size of the farm. Sir John Lawes has calculated the composition of farmyard manure which should be produced in the case of a farm of 400 acres, farmed on the four-course system. He assumes that half of the roots and 100 tons of hay are consumed at the homestead; that the whole of the straw of the corn crops is retained at home as food and litter; that twelve horses have corn equal to 10 lb. of oats per head per day; and that about ten shillings per acre are expended in the purchase of cake for feeding stock. Under these conditions the amount of farmyard manure should be 855 tons (or an average of 8-1/2 tons for each of the 100 acres of root-crop) of fresh undecomposed dung. (For composition, see Appendix, Note XVII., p. 291.) Another method is by taking, as the data of calculation, the number of cattle, horses, sheep, &c., producing the manure. Lloyd considers that a fattening animal requires 3 tons of straw in the year, and makes about 12 tons of manure. A farmer, therefore, should make 8 tons of manure for every acre of that part of his land which, in the four-course rotation, is put down to turnips.
The last method consists in taking as the data the amount of food consumed and litter used in the production of the manure. Of these methods Heiden considers the last as alone satisfactory and trustworthy. Applying this method to the horse, he shows, from experiments, that a little over 47 per cent of the dry matter of its food has been proved to be voided in the solid and liquid excreta. Taking the average percentage of water in the excreta as about 77.5, the percentage of dry matter in the excreta will be 22.5. That is, every pound of dry matter in the food eaten by the horse yields a little over 2 lb. of excrementitious matter. To this of course must be added the amount of straw used as litter, which may be taken at 6.5 lb.
From these data we may calculate the amount of manure produced in a year by a horse, making certain assumptions as to the amount of work performed. This Heiden does by assuming that a horse works 260 days, of twelve hours each, in the course of a year, or 130 whole days, spending 235 days in the stall. Calculating from the above data, he estimates that a well-fed working horse will produce about 50 lb. of manure in a day, or 6.5 tons in a year. Of course this does not necessarily represent all the manure actually produced by the horse, but how much of the remaining portion of the manure actually finds its way to the farm it is impossible to say. According to the 'Book of the Farm,' Division III. p. 98, a farm-horse makes about 12 tons of manure in a year.
It has been calculated that cows void about 48 per cent of the dry matter of their food in the solid and liquid excreta, which contain of water, on an average, 87.5 per cent. That is, every pound of dry matter will furnish 3.84 lb. of total excreta. By adding the necessary amount of straw for litter (which may be taken at one-third the weight of the dry matter of the fodder), Heiden calculates that an ox weighing 1000 lb. should produce 113 lb. of manure in a day, or 20 tons in a year. The 'Book of the Farm,' Division III. p. 98, gives the annual amount at from 10 to 14 tons. According to Wolff, one may assume that on an average the fresh excrements (both liquid and solid) of the common farm animals (with the exception of the pig) contain of every 100 lb. of dry matter in the food consumed about 50 lb., or a half. Estimating the dry matter in the litter used at equal to about 1/4 of the dry matter of the food, this would mean that for every 100 lb. of dry matter consumed in food there would be 75 lb. of dry manure (viz., 50 lb. dry excrements + 25 lb. dry litter), which would yield 300 lb. of farmyard manure in the wet state—i.e., with 75 per cent water. The amount of food daily required per every 1000 lb. of live-weight of the common farm animals may be taken, roughly speaking, at 24 lb. dry food material and 6 lb. of straw as litter. The daily production of manure for 1000 lb. of live-weight would amount, therefore, to 18 lb. of dry, or 72 lb. wet manure. (See Appendix, Note XVII., p. 291.) According to J. C. Morton and Evershed, oxen feeding in boxes require 20 lb. of straw per head per day as litter. An ox, therefore, will make 8 tons of fresh dung in six months, using 32 cwt. of litter. This means that each ton of litter gives 5 tons of fresh dung. It is calculated that nearly twice as much litter must be used in open yards.
[163] It has been calculated that under ordinary circumstances sheep-dung, when allowed to ferment by itself, should do so in about four months, horse-dung in six months, and cow-dung in eight months.
[164] See Appendix, Note XII., p. 286.
[165] See Heiden's 'Düngerlehre,' vol. ii. p. 156.
[166] Warington, 'Chemistry of the Farm,' p. 33.
[167] Recent experiments by Müntz and Girard in France have shown that the loss in sheep excreta from volatilisation of the carbonate of ammonia amounted to over 50 per cent. By the use of straw litter this was reduced to about a half less, and with earth litter one quarter less.
[168] See Appendix, Note XIII., p. 288.
[169] See Appendix, Note XIV., p. 289.
[170] See Appendix, Note XV., p. 290.
[171] For spring application rotten farmyard manure is generally used, because in this condition its fertilising matter is more quickly available. On light land it is best to apply it in the rotten condition shortly before it is likely to be used. (See p. 261.)
[172] The total amount of plant-food in a ton of farmyard manure is together less than 1/20th of its total weight.
[173] See Heiden's 'Düngerlehre,' vol. ii. p. 171.
[174] For full details see Appendix, Note XVI., p. 290.
[175] Storer reproduces these results in his 'Agricultural Chemistry,' vol. ii. p. 21.
[176] This aspect of farmyard manure has been ably stated by Mr F. J. Cooke, a well-known Norfolk farmer. In commenting on the results of the Rothamsted experiments, he says: "It is clear enough that the faith of the farmer in the soil-enriching character of his home-made manure is amply justified; the only question being, indeed, if this quality be not too highly appreciated. It is not, after all, so much by the fattening of our land as by the bounty of the crop grown upon it that we reap the fruit of our exertions. The man of scientific mind keeps his purpose fixed on the production of good crops mainly, and the cheapest way to grow them. The experiments under consideration show that richness of land may be purchased much too dearly, and that richness of crop by no means bears the necessary relation to richness of soil which has sometimes been imagined. We may boast of the 'lasting qualities' of our dung, but the answer of science by these experiments is, that so great is the last that the life of one man may not be long enough to exhaust it. In the extravagant use of dung, therefore, such considerations, amongst many others, as length of purse, as well as length and character of tenure, must clearly be taken into account."
[177] See paper on "Manurial Experiments with Turnips" by author, in 'Transactions of the Highland and Agricultural Society of Scotland;' 1891.
[178] Storer's 'Agricultural Chemistry,' vol. i. p. 498.
[179] Division III. p. 130.
[180] Mr F. J. Cooke, who has already been quoted, has kindly furnished the author with his views on the peculiar functions of farmyard manure as a manure. He says: "I look upon it, broadly speaking, as chiefly of value in restoring to good land, after cropping, those particular advantages which good land alone can give, and in helping better than any other manure, when applied to poor land, to bring it up to the level of good land in those particular merits which belong alone to fine soils. I speak now of an inherent value in good soils, beyond that attaching to them as mere reservoirs of abundant plant-food. For instance, one may supply a poor soil by artificial manure with much more food—and in a highly soluble condition—than is needed by the crop to be grown upon it, and yet not get so good a crop as upon a naturally richer but otherwise similar soil less abundantly filled with immediately available food. This may arise from a more perfect distribution of the plant-food in the rich soil, or from the steady way in which it becomes available to the crop, as well as for other reasons. But whatever the cause, there, I think, is the broad fact of the power of farmyard manure to enrich poor soils, so to speak, more naturally—that is, in a way which makes them more nearly correspond to better soils than artificial manures can."
Hence the indirect benefit to the farmer from farmyard manure is probably greater than its direct value as a mere manure. And the usual provision and use of it amongst all straw-growing farmers is sufficiently justified. The extent, however, to which that course may be beneficially carried, is one of the most important of the many difficult economic and scientific problems which the farmer has to face.
On the economic side must of course be considered the cost of manufacture in individual instances, as ruled by the market value of the straw, and the different circumstances and conditions under which the various farm animals are kept and fed (I have the figures by me of one well-known farmer, which show the cost to him of every ton of home-made manure to be 20s. or more); the price the resultant crops may be expected to command; the cost at the moment of artificial manures, &c., &c. Whilst on the scientific side must be considered the nature of the soil, the particular rotation of crops, &c.
It was, amongst others, just these scientific and yet very definite and practical problems we have tried to throw light on in the series of field experiments conducted for several years by the Norfolk Chamber of Agriculture. (See reprint of summary of same in last year's Report of the Board of Agriculture.)
APPENDIX TO CHAPTER VII.
NOTE I. (p. 225).
Difference in Amount of Excreta voided for Food consumed.
With regard to the difference in the composition of the solid excreta voided by different fattening animals fed on the same amount of food, see Warington's 'Chemistry of the Farm,' p. 125, where it is shown that for equal amount of live-weight, the sheep produces on the same weight of dry food very much more manure than the pig, while the ox produces even more than the sheep. Of course this does not refer to the total amount of manure produced by the different animals, but only to the amount of manure produced from the consumption of equal quantities of food. This would seem to be owing to the greater capacity the pig has for assimilating its food.