MANURE 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 alkaline 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 ; cxre must accordingly be taken to absorb all the urine by the litter. Farmyard manure, it is well known, 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 Wu rtemberg, of farm yard manure in its different stages of decomposition : TABLE V. Average Percentage Composition of Farmyard Manure. Fresh. Moderately Kotten. Thoroughly Rotten. Water 71-0 75-0 79-0 Organic matters 24-6 19-2 14-5 Asli 4-4 5-8 6-5 Potash 100-0 52 ico-o 63 lOO O 50 Soda 15 19 13 Lime 70 88 14 18 18 Phosphoric acid 21 26 30 12 16 13 Chlorine 15 19 16 Silica . . 1-25 l G8 1 70 45 50 58 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 50 per cent. Phosphoric acul 53 ,, Nitrogen 64 ,, Forty tons of dung, according to this estimate, contain in round numbers 448 K> 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 does 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 : TABLE VI. Showing the Loss ivhicli Dung sustains ly Drainnije in Open Yards. ,, , After 12 ,[ rcsh Montis- Manure. Kxposure- Weight of the manure 1652 Amount of water in the manure 1093 ,, dry substances 559 The dry substances consist of A. Soluble organic matters 40 97 B. Soluble mineral matters ,. 2-V43 C. Insoluble organic matters 425-67 D. Insoluble mineral matters Whereof 559-00 A contains nitrogen 3-28 Equal to ammonia 3 98 B contains ni rogtn 6-21 qu:vl to amm< nia 7 54 4-25 9-49 Total amount of nitrogen in manure Equal to ammonia 11 52 The whole immure contained Ammonia in free state Ammonia in the form of salts readily ) decomposed by quicklime ) Total amount of organic matters 406-64 mineral matters 92-36 4-C4 55 1-45 98-40 72-45 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