Classification of manures 131 



that a smell of ammonia ii often noticeable. This 

 means a loss of much valuable nitrogen, and should, 

 if possible, be prevented. 



The loss of ammonia from manure piles is caused 

 by the action of a certain class of bacteria, which de- 

 stroys the organic matter of manure, forming ammonia 

 which passes off as a gas. If the manure pile be pro- 

 perly protected the ammonia is retained and changed 

 into nitrates. The best known method of protecting 

 manure is to compost it. In all cases the manure pile 

 should be under a shed or covering of some sort to 

 protect it from the weather. 



126. Composting. — The decay of manure is always 

 caused by the action of bacteria, and as the manure 

 is warmed the action of the bacteria becomes more 

 rapid. If the manure pile be thoroughly moistened, 

 nitrates are formed by the bacteria just as they are 

 formed in the soil when nitrification takes place. If, 

 however, the warm pile has been exposed to the sun 

 and weather, and has dried out no nitrates are formed, 

 but in their place compounds of ammonia which escape 

 into the air. An unprotected manure pile may in this 

 way become in a short time of almost no value. The 

 nitrates which are formed are easily soluble, and unless 

 absorbed in some way are rapidly drained away from 

 the manure When nitrates are formed in tin 

 if not taken up by plant roots they are partly absorbed 

 and retained by the soil itself; hence the practice of 

 mixing ordinary earth with manure to form a compost 

 heap. Fini I bed il provided from which no drainage 

 can take place, and on this is spread a layer of manure. 



