296 



MICROBIOLOGY OF SOIL 



It will be observed that in the months of November to March the 

 soil temperatures in the two places were nearly the same. On the 

 other hand, in April to October the average temperatures at New 

 Brunswick were for soil 14.5° (58°?.) and for air 22.5" (72°?.), re- 

 spectively; and in July they were 20.0° (68°F.) and 24.5° (76.4°F.) 

 respectively. It will also be observed that there is an unmistakable 

 relation between the corresponding air and soil temperatures. 



As a further illustration of the relation of climate to temperature a 

 comparison may be made of the average daily mean temperatures at 

 Bismarck, North Dakota, for the period 1873-1895, and at Key West, 

 Florida, for the period 1872-1895. 



It is obvious from the figures given here that, because of the im- 

 portant temperature variations of different soil regions, the micro- 

 biological activities must be profoundly modified. ■ But apart from the 

 climatic variations already indicated there are seasonal variations in 

 any particular locaUty that are of great moment for soil microbiological 

 activities. Such differences are demonstrated by the temperatures 

 of 1898 and 1902, taken to a depth of 152 mm. (6 inches), at New 

 Brunswick, N. J. 



In this instance, the season of 1898 was not only earlier, but the 

 temperatures of June to September were sufficiently higher to favor 

 more intense bacterial growth and activity. 



* Recorded in Fahrenheit scale. 



