524 PRINCIPLES OF SOIL MICROBIOLOGY 



in the partial sterilization of soil, or when conditions do not favor 

 nitrification, as with excessive soil acidity, ammonia may accumulate 

 in the soil. 



The intense accumulation of nitrates in places where large quantities 

 of organic matter are allowed to decompose was explained by the 

 chemists of the earlier part of the nineteenth century to be a result 

 of chemical processes. Davy 14 expressed the opinion that nitrates are 

 formed at the expense of the ammonia of the soil and atmospheric 

 oxygen; Liebig demonstrated that atmospheric nitrogen takes no part 

 at all in the process of nitrification. 



The oxidation of ammonia to nitrate can be accomplished by chemi- 

 cal means, especially at high temperatures and in the presence of 

 catalysts, 15 as in the case of the electrolytic oxidation of ammonia in 

 the presence of copper oxyhydrate. 16 Ammonia can be oxidized to 

 nitrate to a limited extent in an atmosphere saturated with ammonia 

 and in the presence of ferric hydrate. 17 Ammonia is also oxidized to 

 nitrite by ultra-violet radiation. 18 According to Weith and Weber, 1 ' 

 hydrogen peroxide and ammonia react with each other giving rise to 

 nitrous acid. The interaction between ozone and ammonia to give 

 ammonium nitrate has been known for several decades: 



(NH 3 ) 2 + 4(0,) -» NH 4 N0 2 + H 2 2 + 4(0 2 ) 

 NH4NO2 + H 2 2 -> NH4NO3 + H 2 



The quantities of nitrite and nitrate formed by chemical agencies 

 are insignificant and of little importance in the soil. In the soil, 



14 Davy, H. Elements of agricultural chemistry. 1814, p. 308. 



16 Sestini, F. Bildung von salpetriger Saure und Nitrifikation als chemischer 

 Prozess im Kulturboden. Landw. Vers. Sta., 60: 103-112. 1904; Mooser, W. 

 Biologisch-chemische Vorgange im Erdboden. Beitrage zur Stickstofffrage. 

 Landw. Vers. Sta., 75: 53-106. 1911. 



18 Traube, W., and Biltz, A. Die Gewinnung von Nitriten und Nitraten durch 

 elektrolytische Oxydation des Ammoniaks bei Gegenwart von Kupferhydroxyd. 

 Ber. deut. chem. Gesell., 39: 166-178. 1906. 



17 Russell, E. J., and Smith, N. On the question whether nitrites or nitrates 

 are produced by non-bacterial processes in the soil. Jour. Agr. Sci., 1: 444-453. 

 1906. 



18 Berthelot, D., and Gaudechon, H. La nitrification par les rayons ultra- 

 violets. Compt. Rend. Acad. Sci., 152: 522-524. 1911. 



19 Weith, W., and Weber, A. Ueber Bildung von Salpetrigsauren Ammoniak 

 aus Wasser und N. Ber. deut. chem. Gesell., 7: 1745-1749. 1874. 



