ANBIAL MANURES. 1 2 1 



ingly in value, and in many cases be deficient in some of the 

 most essential ingredients. 



178. A slight consideration of the nature of the substances 

 which compose the manm'e heap, will show you how much 

 its value may be lessened by the ordinary wasteful practice 

 of the farmers in this country. In the first place, it consists 

 of a mixture of vegetable matters, which have been trodden 

 under the feet of cattle, and saturated with their urine, and 

 therefore in the most favourable condition for undergoing 

 fermentation. In the course of some weeks after the mix- 

 ture has been formed, you find, upon examining the heap, that 

 heat is produced, and that a kind of slow combustion is going 

 on within it. The effect of this fermentation or combustion 

 is to break up the structure of the straw and other vegetable 

 matters present, and, in the escape of the pungent smelling 

 ammonia and other gases which fill the farm-yard with their 

 odours, you perceive that some of the ingredients of the 

 mixture have become volatile, and are escaping into the 

 atmosphere.* 



1 79. Now, every pound of ammonia which escapes, carries 

 with it the nitrogen which would have been sufficient for 

 the growth of 601bs. of com. As the fermentation of the 

 manure proceeds, more and more of the organic matter pre- 

 sent undergoes decomposition, and is converted into volatile 

 gases ; so that, after rotting for several months, its weight 

 is found to have greatly diminished, and it has become a 

 black, friable mass-f Nor is it merely the organic matters 

 of the mixture that are lost. Considerable portions of the 

 excrements of animals readily dissolve in water, and the 

 tissues of the straw, leaves, and other vegetable remains, 

 being broken up by the fermentation, the mineral matters 



* If a piece of moistened red litmus test-paper be brought near a 

 smoking manure heap, it will be rendered hlue^ and a glass rod mois- 

 tened -with spirits of salts (muriatic acid) will be covered with a white 

 crust of sal ammoniac, produced by the union of the acid -with the 

 escaping ammonia. 



f Some instructive experiments made on the continent show us how 

 much manure is wasted by allowing it to remain exposed in heaps. Thus, 

 a hundred loads of jfresh dung were reduced at the end of 



Loads Loads 



81 days, to 73.3, sustaining a loss of 2G.7 



254 „ G4.4 „ 35.6 



384 „ 62.5 „ 37.5 



493 „ 47.2 „ 52.8 



