PRF.VENTION OF LOSS 265 



practice not only reinforces the manure in phosphoric acid 

 content, but also serves to make the rock phosphate avail- 

 able to plants (Section 173). Three or four pounds to each 

 animal every day for horses and cattle is a good amount 

 to use. 



In addition to the leaching away of soluble nitrogenous 

 compounds, a large part of the nitrogen is lost by volatiliza- 

 tion. Since this is due largely to aerobic bacterial action, 

 combined with free circulation of air which allows dissociation 

 of ammonium carbonate, a system which keeps the pile 

 compact and saturated with water, or at least with carbon 

 dioxide, will answer the purpose. This may be accomplished 

 by compacting either in piles or pits, or under the feet of the 

 animals by the so-called deep-stall system. 



If a pile of manure is kept well packed down and 

 thoroughly though not excessively soaked with water or 

 surplus urine, air will not have access to the pile except on 

 the surface, and aerobic decomposition will be reduced to a 

 minimum. By this means nitrogen is not lost to any great 

 extent either as free nitrogen or as ammonia. 



The deep-stall system consists in allowing the manure to 

 be compacted by the feet of animals in stalls where the 

 manure can accumulate and be well tramped down, litter 

 being liberally used. By this means the loss of nitrogen is 

 reduced to about 15 per cent., but the practice is not sani- 

 tary and although used to some extent in Europe is not to be 

 recommended. The saving of nitrogen in manure is not the 

 only thing to be considered in caring for stock. 



(b) Chemical. — In preventing the loss of fertilizing con- 

 stituents from manure by chemical means there is only 

 nitrogen to be considered. Phosphorus and potassium 

 are easily retained by preventing leaching and this is a 

 mechanical means. Nitrogen, on the other hand, is volatile 

 as ammonia and free nitrogen, hence chemicals which 

 form non-volatile compounds of nitrogen, or which prevent 

 complete decomposition, are employed. 



1. Gypsum, Land Plaster. — By using gypsum, CaS0 4 , 

 at the rate of 100 pounds to the ton of manure, or better 

 yet by sprinkling three or four pounds in the stall of each 



