29 



Similarly also in exposed heaps the loss of dry matter is usually 

 proportionally greater than that of nitrogen. 



The loss of nitrogen might occur by 



(a) washing away of soluble nitrogen compounds^ 



(b) volatilisation of ammonia^ 



(c) evolution of nitrogen, 



(d) other ways. 



From the sheltered heap (a) is excluded. 



It is further shown that (b) can hardly account for the observed 

 losses in the heap, and certainly not for those in the laboratory experi- 

 ments, where the extent of volatilisation was measured and found to be 

 only small. An evolution of nitrogen has been demonstrated in the 

 laboratory experiment and presumably a similar change goes on in the 

 heap. 



In the laboratory experiments decomposition never proceeded very 

 far, the maximum losses being 17 per cent, of dry matter, 30 per cent, 

 of complex nitrogen compounds, and ^;^ per cent, of total nitrogen. 



In our heap experiments we find this last fraction of complex 

 nitrogen compounds, representing 50 to 60 per cent, of the original 

 total nitrogen, only decomposes very slowly indeed. 



XV. " 0)1 Making and Storing Farmyard Manure. E. J. 

 Russell and E. H. Richards. Journal of the Royal 

 Agricultural Society, 191 7. 77, i-35- 



In this paper the above results are applied to the practical problem 

 of storing farmyard manure. 



The objects to aim at in a manure heap are to secure 

 {a) as much dry matter, 



(b) as much ammonia, and 



(c) as Httle loss of nitrogen as possible. 



The laboratory experiments show that these objects can all be 

 attained by storing the manure heaps under anaerobic conditions {i.e., 

 with complete exclusion of air) at about 26° C. Under these circum- 

 stances there is a formation of ammonia and no loss of nitrogen, although 

 some loss of dry matter occurs. 



The farm experiments, on the other hand, show that these desirable 

 results are not attained in manure heaps, no matter how well put up. 

 However compact the heap some nitrogen is always lost and there is 

 never an accumulation, but commonly a loss of ammonia. 



Apparently the requisite conditions can only be attained in a w^ater- 

 tight pit or tank that could be closed so as to keep out oxygen and 

 keep in the carbon dioxide produced by fermentation. This would be 

 the ideal method for storing farmyard manure. But as this ideal 

 method presents practical difficulties, we must see how nearly the best 

 methods of practice approximate to it, and whether any further 

 improvements can be suggested. 



Two cases arise : 



I. — Manure left undisturbed under the beasts, e.g., manure made 

 in covered yards or stalls by fatting beasts. 



2. — Manure thrown out daily, e.g., manure made from dairy stock 

 or from the horse stables. 



