FARMYARD MANURE. 27 



11. In the fermentation of dung a very considerable proportion 

 of the organic matters in fresh manure is dissipated into the air 

 in the form of carbonic acid and other gases. 



12. Properly regulated, however, the fermentation of dung is 

 not attended with any great loss of nitrogen nor of saline mineral 

 matters. 



13. During the fermentation of dung, ulmic, humic, and other 

 organic acids are formed, as well as gypsum, which fix the am- 

 monia generated in the decomposition of the nitrogenized con- 

 stituents of dung. 



14. During the fermentation of dung the phosphate of lime 

 which it contains is rendered more soluble than in fresh manure. 



15. In the interior and heated portions of manure-heaps am- 

 monia is given off; but, on passing into the external and cold 

 layers of dungheaps, the free ammonia is retained in the heap. 



16. Ammonia is not given off from the surface of well-com- 

 pressed dungheaps, but on turning manure-heaps it is wasted in 

 appreciable quantities. Dungheaps for this reason should not be 

 turned more frequently than absolutely necessary. 



17. No advantage appears to result from carrying on the fer- 

 mentation of dung too far, but every disadvantage. 



18. Farmyard manure becomes deteriorated in value when kept 

 in heaps exposed to the weather the more the longer it is kept. 



19. The loss in manuring matters, which is incurred in keeping 

 manure-heaps exposed to the weather, is not so much due to the 

 volatilization of ammonia as to the removal of ammoniacal salts, 

 soluble nitrogenized organic matters, and valuable mineral mat- 

 ters, by the rain which falls in the period during which the 

 manure is kept. 



20. If rain is excluded from dungheaps, or little rain falls at 

 a time, the loss in ammonia is trifling, and no saline matters of 

 course are removed ; but if much rain falls, especially if it 

 descends in heavy showers upon the dungheap, a serious loss in 

 ammonia, soluble organic matters, phosphate of lime, and salts 

 of potash is incurred, and the manure becomes rapidly deterio- 

 rated in value, whilst at the same time it is diminished in weight. 



21. Well-rotten dung is more readily affected by the deterio- 

 rating influence of rain than fresh manure. 



22. Practically speaking, all the essentially valuable manuring 

 constituents are preserved by keeping farmyard manure under 

 cover. 



23. If the animals have been supplied with plenty of litter, 

 fresh dung contains an insufficient quantity of water to induce an 

 active fermentation. In this case fresh dung cannot be properly 

 fermented under cover, except water or liquid manure is pumped 

 over the heap from time to time. 



Where much straw is used in the manufacture of dung, and no 



