CHAPTER XX. 

 AMMONIFICATION. 



IN the preceding chapter it was shown that one of the final prod- 

 ucts resulting from putrefaction, fermentation, and decay is 

 ammonia. The production of ammonia through the intervention of 

 microorganisms is known as ammonification. The speed with which 

 this ammonia is formed within a soil varies with the physical and 

 chemical composition of the soil together with the number and 

 physiological efficiency of the various organisms taking part in the 

 process. 



Although it has been known for some time that small quantities 

 of ammonia occur in all arable soil, its formation was not known 

 to be due to a biological process until 1893 when Muntz and Coudon 

 demonstrated that ammonia is no longer formed in soils sterilized 

 by heat. They, together with Kayser, isolated from soil two species 

 of Bacterium, one of Bacillus, two of Micrococcus, and two of molds 

 all of which produced ammonia in veal bouillon, and all but one 

 (a micrococcus) gave the same results in soil. From these results 

 they concluded that the formation of ammonia in the soil is the 

 result exclusively of the conjoint activity of numerous lower organ- 

 isms of very widely different characters. 



This conclusion was confirmed the same year by Marchal who 

 isolated from the soil the species of microorganisms (molds, yeast, 

 and bacteria) which were the most prevalent, and determined which 

 of these had the power of transforming nitrogenous material into 

 ammonia. Of 31 species tested, 17 displayed a strong ammonify- 

 ing power. Most of the others displayed a smaller but none the 

 less distinct ammonifying power. Molds and yeast w r ere also found 

 to produce ammonia. On inoculation into a solution containing 

 1.365 gms. of organic matter per liter the various organisms were 

 found to transform the following proportion of nitrogen into am- 

 monia in twenty days : 



B. mycoides 46 



N 1 39 



Proteus vulgaris 36 



B. mesenterius vulgatus 29 



Sarcina lutea 27 



B. janthinus 23 



B. subtilis ' 19 



The B. mycoides was selected by him for special investigation. 

 This organism is found very widely distributed in nature. It is 



