NITRIFICATION 



The transformation of complex organic nitrogenous 

 material which occurs in the soils takes place in three 

 stages, namely : 



1. The production of ammonium compounds from 



the proteins, amino-acids, and other organic 

 bodies present. 



2. The oxidation of the ammonium salts thus formed 



into nitrites. 



3. A further oxidation of nitrites into nitrates. 

 The term nitrification is usually restricted to the two 



latter stages, that is, to the oxidation of ammonium 

 compounds into nitrates. No organisms are known 

 which will directly nitrify proteins, amino-acids, urea, or 

 similar nitrogenous substances ; these must be decom- 

 posed first and ammonium compounds prepared from 

 them, the latter being subsequently acted on by the 

 specific nitrifying bacteria. 



The preliminary breaking down of the complex 

 organic matter with the formation of ammonium salts is 

 effected by a large number of different kinds of bacteria. 

 Most of the putrefactive group are concerned in the 

 work ; bacteria commonly present in soil which are 

 specially active in this direction are Bs. mycoides, 

 Bs. putidus, Bs. mesentericus vulgatus, Proteus vulgaris, 

 Bact. fluorescent liquefaciens, and Micrococcus candicans. 

 Marchal found that Bs. mycoides liberated 46 per cent. 

 of the nitrogen of egg-albumen as ammonia, Proteus 

 vulgaris 36 per cent., and Bs. vulgatus 30 per cent, in 

 twenty days. In addition to bacteria, which are most 

 efficient in neutral or alkaline soils containing little 

 organic matter, certain fungi, such as Penidllium glaucwn, 

 Mucor Mucedo, M. racemosus, and species of Botrytis 

 and Torula^ are also responsible for the breaking down 



