426 MICROBIOLOGY OF SOIL 



great extent aluminum is affected by these reactions, for in the decompo- 

 sition of feldspar, kaolinite is one of the important products formed. 

 Hence, bacteria become a factor of considerable importance in the forma- 

 tion of hydrated silicates of aluminum, at least, in the presence of 

 organic matter. Moreover, it is recognized in the ceramic industries 

 that after it is dug clay must undergo ripening in order to be suitable 

 for certain purposes. The ripening process involves the activities of 

 bacteria. Unfortunately very little is known about the reactions that 

 occur in the ripening of clay. 



As to manganese and copper there is scarcely any experimental evi- 

 dence available as to the part played by their compounds in the soil, 

 particularly in so far as they affect microorganic life. To some extent, 

 it is known that where Bordeaux mixture has been employed for spray- 

 ing potatoes, cranberries, fruit trees, etc., plant growth is subsequently 

 stimulated to a striking extent. In view of the very slight quantities of 

 copper that are actually added to the soil by these sprays, it is possible 

 that the effects noted are caused by stimulated or changed microbial 

 activities. This view finds some support in the influence exerted by 

 copper sulphate on the growth of algae in lakes, ponds, and shallow 

 streams. 



It has also been reported that the decomposition of complex silicates 

 has been effected from powdered minerals by nitrite bacteria. 



ANTAGONISM 



A subject which bids fair to become a fertile source of investigation 

 is the application of certain biochemical laws, as established by Loeb 

 and Osterhout in the animal and plant worlds respectively, to the 

 effect of salts on the physiological efficiency of soil bacteria in pure and 

 mixed cultures, as well as in the soil. C. B. Lipman has advanced in- 

 formation concerning the antagonism between anions as related to 

 nitrogen transformations in soils, with special reference to the reclama- 

 tion of alkali lands. Antagonism exists to a more or less marked 

 extent between anions of alkali salts (as for example between NaCl 

 and Na 2 SO 4 , Na 2 CO 3 and Na 2 SO 4 and between NaCl and Na 2 CO 3 ) 

 when the ammonifying or nitrifying powers of the soil are employed 

 as criteria. The nitrogen-fixing flora, however, is not similarly 

 affected, apparently offering greater resistance. The practical sug- 



