224 FARMYARD MANURE [chap. 



value it on the unit system (see p. 348), the result of 

 which would be somewhat as follows : — 

 Farmyard manure contains — 



0'6 per cent. Nitrogen at 12s. . ,= £072, 



0-3 per cent. Phosphoric Acid at 3s. . = o oil 



0-5 per cent. Potash at 4s. . . = 020 



Value per ton . = ;^o 10 i 



Much weight cannot, however, be attached to such a 

 valuation, because the unit values are taken from con- 

 centrated manures and do not apply to dung ; for 

 example, nitrogen in waste materials like shoddy can 

 often be obtained at half the price paid for it in 

 sulphate of ammonia or nitrate of soda, and considering 

 the slow availability of much of the nitrogen in dung its 

 unit value should be much below 12s. On the other hand, 

 the organic matter supplied in the farmyard manure is 

 not valued ; yet it is for the effect of this organic matter 

 on the texture of the soil that farmyard manure is most 

 generally required. The cost of handling farmyard 

 manure, which is so much greater than it is for an 

 equivalent amount of artificial fertiliser, should also be 

 taken into comparison but cannot well be estimated, 

 because it will vary on each farm. 



While it is thus practically impossible to value farm- 

 yard manure on its composition, a proper system of 

 book-keeping will show what it costs to make, in a 

 manner that is independent of the profit and loss 

 upon the live stock. In this way a farmer can form 

 for himself a clear idea of the economics of dung-making 

 as compared with the purchase of either town manure or 

 artificial fertilisers. The most valid principle on which 

 a cost can be worked out, and one which does justice 

 equally to the live stock and to the manure, is to 



