272 Bacteria in Relation to Country Life 



Bare fallows and nitrogen in the soil. — The partisans 

 of bare fallows have tried, within recent years, to justify 

 the practice by the claim that, during the period of 

 fallowing, the nitrogen-fixing bacteria, particularly the 

 azotobacter species, increase in numbers and add con- 

 siderable quantities of nitrogen to the soil. The German 

 estate owner, Caron, the originator of alinit, noted an 

 increase of nitrogen in his soil and ascribed it to the 

 influence of bare fallows. Other observations made in 

 various localities, are in accord with this in so far as 

 gains of nitrogen in bare soils are concerned. To what 

 extent the activities of the non-symbiotic nitrogen- 

 fixing bacteria are intensified by the process of fallowing 

 is still to be determined. 



Bacterial changes. — There is no doubt, however, that 

 the changes in the bacterial relations in the soil, due to 

 fallowing, are far-reaching. It was shown by the investi- 

 gations of Hiltner and Stormer that under normal con- 

 ditions the various groups of soil bacteria establish a 

 certain balance among themselves, a balance that is 

 partly or wholly destroyed by changed soil conditions. 

 Thus, when the soil is treated with antiseptics, like 

 carbon bisulfide, chloroform, or ether, the bacteria are 

 decimated in their numbers. Some of the species are 

 injured by this treatment to a greater extent than others. 

 After the destructive action of the antiseptic had 

 disappeared, the bacteria increase again to enormous 

 numbers, exceeding by many times the normal quantity 

 in cultivated soils. Furthermore, the new development 

 under such conditions does not show the same relations 

 among the various groups. Similarly, the process of 



