1921.] Artificial Farmyard Manure. 407 



ammuiiia, or cumpounds giving free ammonia such as urea or 

 peptone, or in the presence of sodium 'hydroxide or sodium car- 

 bonate, the colour is dark brown, and differs only slightly 

 from the natural product. The liquid, which is gradually 

 expressed from the fermenting straw as more and more dry matter 

 is lost by fermentation, has a dark brown colour and a smell which 

 is in(Hstin,L!;uishable from stale urine. 



Application of Results to the Production of Ordinary 

 Farmyard Manure. — Since it has been possible to produce 

 material identical in physical properties with well-rotted farmyard 

 manure, differing only in chemical composition in so far as the 

 latter contains appreciable quantities of phosphorus and potash 

 derived from foods consumed by the animal, the possibility sug- 

 gested itself that the results might be applicable to the making of 

 ordinary farmyard manure and led to an inquiry in this direction. 



Of the three constituents ordinarily present in manure — urine, 

 faeces and straw — the fcTces appears to contribute to the physical 

 character of the product only, since manure can be produced with- 

 out their presence. Moreover, definite experiments have shown 

 that, chemically, fa3cal nitrogen is to a great extent inert and 

 is not capable of contributing to the decomposition of straw to 

 any degree comparable with urine nitrogen. On the contrary, 

 certain methods of feeding farm animals, and particularly of 

 horses, sometimes lead to the production of faeces containing 

 quantities of readily available carbohydrates, and it has been 

 shown* that such faeces are capable of supporting the fixation of 

 atmospheric nitrogen. There is every reason to suppose, there- 

 fore, that the faecal portion of the manure heap inclines 

 slightly in the direction of itself requiring nitrogen rather than 

 acting as a source of nitrogen for the decomposition of straw. 

 With the above exception of some horse f.ioces, the solid excre- 

 ments of farm animals may be regarded as having reached a state 

 similar to that observed above in fermented straw, i.e., 

 containing roughly 2 per cent, of nitrogen in the dry 

 matter. This is borne out by the following mean figures which 

 have been obtained from various sources: — 



Horse ffeces (mean of 8 records) = 2*00 per cent. X. in dry matter. 



Cow „ ( „ „ 11 ., ) = 1-H8 " .. 



Slieep ( „ „ 7 „ ) = M'-i „ 



AvercKj-e of '2() records = 1 •'.).') ,, ,, 



We thus see that during the process of digestion, and also 

 possibly ])y virture of bacterial action in the intestinal tracts, the 



* Jour. Acjric. ScL, 1917, Vol. VITI, p. 299. 



