554 The Storage of Farmyard Manure 



(b) volatilisation of ammonia, 



(c) evolution of nitrogen, 



(d) other ways. 



From the sheltered heap (a) is excluded. 



It is further shown that (6) 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. In the laboratory experiment an evolution of nitrogen 

 has been demonstrated and presumably a similar change goes on in 

 the heap. 



10. In the laboratory experiments decomposition never proceeded 

 very far, the maximum losses being 17 % of dry matter, 30 % of 

 complex nitrogen compounds, and 33 % of total nitrogen. 



11. In our heap experiments we find this last fraction of complex 

 nitrogen compounds, representing 50 to 60 % of the original total nitro- 

 gen, only decomposes very slowly indeed. 



We can now come to the application of these results to the practical 

 problem of storing farmyard manure. It is unnecessary for us to go 

 into detail as this has already been done elsewhere^. We may, however, 

 indicate the general outlines. In the first instance we must be quite 

 clear as to what is wanted. This can only be determined by field 

 trials, and our experiments recorded on pp. 505-507 show that the main 

 factors determining the value of farmyard manure are the total nitrogen 

 and the ammonia : indeed it is possible to evaluate the manures on this 

 basis provided the ammonia figures are adequately "weighted." The 

 total dry matter is of obvious importance in view of physical effects, 

 but we have no information as to the value of any particular non- 

 nitrogenous constituent. SjoUema and de Wildt regarded the pentosans 

 as undesirable on the theoretical ground that they favour denitrification, 

 but there is no sufficient evidence that the loss of nitrogen would be 

 less without them. 



The objects to aim at in a manure heap must be to secure 



(1) as much dry matter, 



(2) as much ammonia, and 



(3) as little loss of nitrogen as possible. 



Now the laboratory experiments show that these objects can all be 

 attained by storing the manure heaps under anaerobic conditions at 

 about 26° C. There is a considerable formation of ammonia and no 

 loss of nitrogen, although some loss of dry matter occurs. 

 ' 1 Journ. Roy. Agric. Soc 1917, 77, 1-35. 



