FORMATION OF AMMONIA BY SOIL MICROBES 133 



TABLE 31 



Influence of Starch and Sucrose upon Ammonia Formation from 

 Dried Blood* (from Lipman) 



* Dried blood containing 155 mgm. of nitrogen added to 100 gm. of soil 



The amount of ammonia formed from the decomposition of 

 organic matter depends upon the following important factors: (1) 

 the composition of the organic material itself, with particular 

 regard to its nitrogen content; (2) the organisms concerned in the 

 decomposition; (3) the prevailing environmental conditions; (4) 

 period of decomposition. 



Organic materials of different origin decompose with different 

 degrees of rapidity. Even the decomposition of the same plant 

 will depend upon its age. The nature and abundance of the non- 

 nitrogenous complexes in the plant, such as sugars, cellulose, 

 hemicelluloses, waxes, resins, lignin, tannins, and cutins, will 

 determine to a large extent the rapidity of decomposition. The 

 rapidity of decomposition of the readily available sources of 

 energy, such as the sugars, starches, pentosans and other hemi- 

 celluloses, and cellulose, will influence the rapidity of decomposi- 

 tion of the proteins and the amount of ammonia reassimilated by 

 the organisms or left in the soil. A young plant decomposes more 

 rapidly than an old plant, because the young plant is richer in 

 readily decomposable substances (sugars, amino acids, phos- 

 phatides) and poorer in slowly decomposable substances (lignin, 

 tannins, waxes, resins). For similar reasons the leaves of some 

 trees decompose more readily than the leaves of others. 



The nitrogen content of a substance is equally important in 



