28 THE ROYAL SOCIETY OF CANADA 



Table lie. 

 Sod covered field seven years old. Moisture Content at Different Depths, 



Date 



Depth of 



Frost Snow 



4" 



12" 



16" 



20" 



27' 



Jan. 

 Feb. 



Mar. 

 April 



1917 

 22. . . 



8. .. 

 12. .. 

 19. .. 

 12... 



2... 

 16... 



15... 

 19... 

 19... 

 12... 



0" 

 7" 

 16" 

 26" 



12" 



4"_9" 



0" 



18" 

 16" 









 14" 







0" 



21-7 

 20-6 



28-2 



Feb. 



Mar. 



1" 

 3" 

 1" 



32 

 30 

 36 

 26 



18-0 

 19-6 

 16-5 

 24-0 



15 

 18-6 

 11-5 

 17-6 



19-6 



15-5 



The lawn from which the samples were taken was poor and 

 gravelly. During January large numbers of bacteria were counted, 

 especially in the surface layer. The heavy snow layer had so far 

 protected the soil from the severe frost. This increase in bacteria 

 during January was also observed in the first experiment and is here 

 probably due to the same cause, the decomposition by bacteria of 

 raw material (grass roots and clover roots) . 



In the beginning of February a plot of about 400 square feet was 

 cleared of snow and kept clear until the 22nd February, during which 

 time the frost penetrated 26 inches. The bacteria decreased steadily 

 in numbers in the frozen soil and the bacterial count was low compared 

 with the bacteria observed on soil of the same field which was not 

 frozen. At the 16" level of sampling the first decrease was followed by 

 a gradual increase, which continued until the soil thawed. It is 

 difficult to draw inferences from one isolated set of results, but a 

 probable explanation is that the severe frost acting on soil containing 

 only a moderate percentage of water checked bacterial activities. 

 At a depth of 16 inches the influence of the frost was slight, and bacteria 

 could increase in the frozen soil. 



Conclusions. 



1. Large numbers of bacteria were obtained from unfrozen soil under 



a lawn during the month of January. 



2. Severe frost prevented bacterial development in frozen soils. 



3. As soon as the soil thawed the bacteria decreased in numbers. 



