INFLUENCE OF STABLE MANURE 213 



organic matter, which is further increased by strav/ and similar 

 forms of bedding material. In the decomposition of these organic 

 substances, considerable nitrogen becomes stored away in micro- 

 bial cells. These factors preclude the rapid formation of ammonia 

 from sohd excreta and result in the persistence of the organic 

 matter in soils for extended periods of time, during which the 

 nitrogen slowly but continuously becomes liberated in forms 

 available to higher plants — a very important factor in soil fer- 

 tihty. 



The losses of nitrogen from composting manure are associated 

 with transformations of the urea which is contained in the liquid 

 excreta. So much ammonia is rapidly formed that the reaction 

 becomes sufficiently alkaline to permit the volatilization of some 

 of the ammonia. The ammonia which remains in the compost 

 may be further transformed to nitrate, and, as the nitrate may 

 pass to certain regions of the mass of organic matter where condi- 

 tions are favorable for reduction, the nitrate may be broken down 

 to gaseous nitrogen or oxides of nitrogen and become dissipated 

 into the atmosphere. 



The control of such losses of nitrogen is based on several dif- 

 ferent principles. The losses of ammonia can be prevented by the 

 addition of acid-reacting substances such as superphosphate, sul- 

 furic acid, or sulfur. The fact that under these conditions super- 

 phosphate reverts to the more insoluble phosphates somewhat 

 decreases the desirability of such treatments. In order to ehm- 

 inate the losses of nitrogen through denitrification the manure is 

 so handled as to prevent the formation of nitrate. Since anaerobic 

 conditions prevent nitrate formation, manures are frequently 

 packed tightly, kept in tight pits and otherwise handled to prevent 

 appreciable penetration of air. The addition of disinfectants pre- 

 vents excessive microbial activity but is not generally practical. 



By hastening the processes of decomposition of the carbohy- 

 drates in the manure, the conversion of the ammoniacal nitrogen 

 into insoluble forms is accelerated by microorganisms, as they 

 transform the nitrogen into their cell substance. These processes 

 are frequently based upon the acceleration of the decomposition 

 by high temperatures. Preliminary aerobic conditions favor rapid 

 decomposition. Subsequent tight packing of the manure results in 

 heating. Under these conditions the temperature rises to about 

 65° C, and the transformation of the carbohydrates is sufficiently 



