776 



PRINCIPLES OF SOIL MICROBIOLOGY 



bacteria isolated from soils of colder climates being capable of growing 

 at lower temperatures than bacteria isolated from soils of warm 

 climates. 24 



SO 25 30 



Percent of Water 



Fig. 72. Influence of moisture and potassium salts upon nitrate accumulation 

 in the soil (from Greaves and Carter). 



Ammonia formation takes place between 15° and 60°C, the thermo- 

 philic organisms being very active in this respect. Nitrification takes 

 place at 15° to 40°C, the optimum being at 35° or a little higher (fig. 



24 Mischustin, E. The analysis of temperature conditions of bacterial proc- 

 esses in the soil in connection with the adaptation of bacteria to climate. Potch- 

 voviedienie., 20: 43-67. 1925. 



