CELLULOSE FERMENTATION 189 



ganic materials in that it leads to the formation of complex com- 

 pounds from carbon dioxid, hydrogen, and oxygen. 



The cellulose ferments also perform other direct functions in 

 the soil, as for instance in the liberating of plant-food which is 

 bound up in the residues of plants. Heinze has very recently 

 ascribed to bacterial activities much of the benefits obtained from 

 summer fallovi^ing. In quantitative studies he found them to be 

 more numerous in fallov^ soil than in cropped soil, and he thinks 

 it is due to their activities in rendering the cellulose more suitable 

 as a carbon supply for the Azotobacter that causes the increase of 

 soil nitrogen in fallow land noted by a number of recent workers. 

 Hence, they are the organisms which decompose the cellulose of 

 straw so it can be utilized by the Azotobacter in the fixation of 

 atmospheric nitrogen. Now, investigations have shown that under 

 suitable conditions the Azotobacter may fix 325 mgm. of nitrogen 

 for every 100 gm. of straw decomposed. At this rate there would 

 be a gain of seven pounds of nitrogen for every ton of straw 

 utilized. This, in addition to other beneficial effects, the farmer 

 is losing when he burns his straw. 



