1 62 AGRICULTURAL BACTERIOLOGY. 



result of the combined action of the legumes and the soil 

 bacteria is the fixation of large amounts of atmospheric 

 nitrogen. 



Which of the two factors of nitrogen fixation is the more 

 important in restoring the nitrogen to the soil can at present 

 hardly be stated. There is beginning to be evidence that the 

 direct fixation by bacteria, independent of legumes, is of far 

 more importance than it was thought a short time ago. Obser- 

 vation has certainly shown that soil which is cultivated without 

 the aid of legumes may hold its nitrogen content fairly well, 

 and this points to the conclusion that the direct fixation of 

 nitrogen, independent of legumes, is of very great significance, 

 and possibly the greatest factor concerned in nitrogen fixation. 



We thus see that the whole problem of the soil fertility is 

 inextricably woven with bacterial fermentation. From the 

 origin of the soil, through its use by plants and the subsequent 

 destruction to their original condition of the products formed, 

 we find nearly every step accompanied by bacterial action. The 

 continued fertility of the soil is thus associated with bacterial 

 life. In the future the problem of the proper treatment of soil 

 for the use of agriculture will be, in a very large degree, a prob- 

 lem of the proper control of bacteria. Agriculturists must 

 learn to stimulate the bacterial actions which are advantageous 

 and check those which arc disadvantageous, if they would in- 

 sure the continuance of soil fertility. 



