1/4 .SOILS AND FERTILIZERS 



number of volatile compounds and in loss of manurial 

 value. When urea ferments, ammonium carbonate, a 

 volatile product, results ; and where the proteids of ma- 

 nure ferment, ammonia is formed, which combines with 

 the carbon dioxide, always present in stables in liberal 

 amounts as a product of respiration, to form ammonium 

 carbonate, a volatile compound. When the stable at- 

 mosphere becomes charged with ammonium carbonate, 

 some of it is deposited on the walls of the stable, 

 forming a white coating. The white coating found 

 on harnesses and carriages stored in poorly ventilated 

 stables is ammonium carbonate. Accumulations of 

 manure in the stable and poor ventilation are the condi- 

 tions favorable to its production. 



195. Human Excrements. The use of human excre- 

 ments as manure is sometimes advised, and in some 

 countries they are extensively so utilized. When fresh, 

 they may contain a high per cent of nitrogen and phos- 

 phoric acid ; but when fermented, a loss of nitrogen has 

 occurred. Heiden estimates 1000 pounds a year of 

 excrements per person, containing $2.25 worth of fertil- 

 ity. 59 For sanitary reasons, human excrements should 

 be used as manure with 1 great care, and it is doubtful, 

 with the abundance and cheapness of plant food, 

 whether the practice is advisable. About 1840 Leibig 

 expressed the fear that the essential elements of plant 

 food would accumulate in the vicinity of large cities and 

 be wasted, and that in time there would be a decline in 



