PRESERVATION OF MANURE. 127 



loss of nitrogen from dung, analysed immediately after the 

 fattening animals were removed, was small, amounting to 

 about 13-25% of the original amount, and was about the same 

 in summer as in winter. If, however, the manure was left for 

 four weeks in the stall after the animals had been removed, 

 the loss in warm weather amounted to 34-8% of the whole. 

 In open dung heaps the loss of nitrogen observed was 37'4 % 

 of the total, while in a parallel experiment in a covered heap 

 36 - 9 % of the total nitrogen was lost ; but the covered heap 

 held manure containing 70% of water, while the open one 

 contained 78 %. The large loss of nitrogen from the covered 

 heap is due to the higher temperature and drier state of the 

 dung, favouring the volatilisation of ammonia. An addition of 

 30 % of marl to the manure reduced the loss of nitrogen from 

 22-6%, to 9-9%, and a mixture of 30% marl and 2% of turf 

 litter reduced it to 6'1 %. The best result was obtained by the 

 addition of 6% of sodium hydrogen sulphate, NaHS0 4 (con- 

 taining 1'5% of free acid), when the loss was diminished to 

 1'3% of the nitrogen originally present. 



The action of free sulphuric acid in preventing loss of nitro- 

 gen is partly attributable to its combining with the ammonia 

 and partly to its preventing the growth of denitrifying bacteria. 



The application of fresh manure to the soil probably leads 

 to a greater conservation of its nitrogen, but there is con- 

 siderable risk of excessive denitrification being set up in the 

 soil, both by the large amount of oxidisable carbonaceous 

 matter and the numerous denitrifying organisms which are 

 present in straw and the faeces of most animals, and this 

 denitrification may extend to the nitrates already present or 

 being produced in the soil. Well-rotted manure, on the other 

 hand, though it may have lost some of its nitrogen, will be 

 much less likely to bring about denitrification. It would 

 seem, therefore, best to favour the fermentations which de- 

 stroy carbonaceous matter, while attempting to retain by 

 absorption in peat moss or other porous material the ammonia 

 which volatilises. In this way the denitrifying organisms will 

 be quickly deprived of their favourable environment, and their 

 destructive effects, both in the manure heap and subsequently 

 in the soil, will be weakened. 



