[vanderleck] 



BACTERIA OF FROZEN SOILS 



Rink Experiment, 



21 



Average number of bacteria (in millions) per gram of soil at different depths 

 on different media. 



The bacterial content of rink soil in 1918 is slightly lower than the 

 year before, probably due to the more severe frost. Also the Rink 

 figures are lower than the ones obtained in Experiment II. The plot 

 in II was only kept clear of snow until February, whilst the Rink 

 was exposed to the frost action throughout the winter. 



Discussion. 



In general the results obtained were disappointing, as the early and 

 severe frost checked any bacterial action. However, winter condi- 

 tions over the greater part of Canada are as encountered in this ex- 

 periment, and from this systematic fortnightly soil analysis we can 

 conclude that in winter no changes take place in the soil and that 

 plant and crop remain during the winter in unchanged condition. 



How far the millions of bacteria present in the frozen 

 soil exercise any action at all depends on the kind of enzyme 

 which they produce. An extra-cellular enzyme will act as long as 

 the bacteria are alive, but for the influence of an intra-cellular enzyme 

 active growth is necessary. This point needs careful study, but a 

 superficial examination has indicated that ammonification and 

 denitrification are produced by extra-cellular and nitrification by 

 intra-cellular enzyme action. This would mean that ammonifica- 

 tion and denitrification will continue in frozen soils even when further 

 bacterial development is at a standstill, whilst nitrification is impos- 

 sible. 



The conclusions given last year stand unchallenged by any data 

 given in this paper, and as they were mentioned in the introduction 

 no further reference to them is necessary. 



