412 THE PRINCIPLES OF SOIL MANAGEMENT 



rate of ammonification. A slightly acid reaction in the 

 liquid produced the maximum activity, but in a neu- 

 tral or even slightly acid medium the process was 

 continued, although much less actively. 



He found that B. mycoides was also capable of 

 ammonifying casein, fibrin, legumin, glutin, myosin, 

 serin, peptones, creatin, leucin, tyrosin and asparagin, 

 but not urea and ammonium salts. 



280. Nitrification. Some agricultural plants can 

 utilize ammonium salts as a source of nitrogen. This 

 has been determined for maize, oats, barley and po- 

 tatoes. Other plants, such as beets, show a decided 

 preference for nitrogen in the form of nitrates. Whether 

 any of the common crops can thrive as well on ammo- 

 nium salts as upon nitrates has not been finally demon- 

 strated. In all arable soils the transformation of 

 nitrogen does not stop with its conversion into am- 

 monia, but proceeds by an oxidation process to the 

 formation of first nitrous and then nitric acids. This 

 may be considered to proceed according to the fol- 

 lowing equations: 



2NH 3 + 30, = 2HN0 2 + 2H 2 0. 

 2HN0 2 + 2 = 2HN0 3 . 



The acid in either case combines with one of the bases 

 of the soil, usually calcium, so that we have calcium 

 nitrate resulting. 



Each of these steps is brought about by a distinct 

 bacterium, but they are closely related. Collectively 

 they are called nitro-bacteria. Nitrosomonas and 

 Nitrosococcus are the bacteria concerned in the 



