478 SOIL SCIENCE 



If cellulose undergoes a direct gaseous fermentation in which a large 

 part or all of the carbon is returned to the air in the first decomposition 

 processes, the addition of cellulose to the soil would undoubtedly be of 

 far less value than if the decomposition products formed by the cellulose- 

 dissolving bacteria were non-volatile and remain in the soil, where they 

 may assist in maintaining the humus content or may serve as a source of 

 energy for important groups of bacteria, such as the nitrogen fixing or- 

 ganisms. 



It is well known that fermentation processes in the soil resulting in a 

 decomposition of the organic matter may give rise to large quantities of 

 CO2 and CH4. However, we have been unable to show that these com- 

 pounds are due to the activity of cellulose-dissolving bacteria. None of 

 the cellulose-dissolving forms studied in our investigations give rise to 

 gaseous products in cellulose or sugar solutions in which they make a 

 luxuriant growth. Under natural conditions the compounds formed by 

 the cellulose-dissolving bacteria will of course be seized upon by a host 

 of other microorganisms and split up into simple compounds. In some 

 soils the destruction may be extremely rapid and complete, resulting in 

 the formation of little humus ; under such conditions a very large per- 

 centage of the carbon in the cellulose is quickly liberated as CO^. How- 

 ever, the COo formed is presumably due in all cases to secondary fermen- 

 tations by the action of the organisms upon the products produced by the 

 cellulose-dissolving organism. Likewise, the organic acids noted by 

 early investigators were, for the most part at least, presumably due to 

 secondary fermentation and not to the action of the cellulose-dissolving 

 forms. 



The influence of the products of bacterial activity in rendering soluble 

 various essential mineral constituents of the soil has come to be recog- 

 nized as of considerable importance in maintaining the fertility of soils. 

 It would seem that the insoluble compounds of potassium, phosphorus, 

 magnesium, calcium, iron, sulphur, and even silicon may be rendered 

 soluble through the production of carbon dioxide and organic acids 

 which result from the decomposition of cellulose and other organic mat- 

 ter in soils. It is well known that limestones are quickly dissolved by 

 carbonated waters, even granite and rocks related to it are attacked be- 

 cause of the feldspar minerals which contain potash, sodium and calcium 

 together with aluminum. The results of this action would seem to be 

 highly important in many western soils as the liberation of the aluminum 

 results in the formation of clay which has an important influence on the 

 physical condition of the soil, while the potassium is one of the essential 

 nutrients of plant growth. 



