276 



Journal of Agriculture. Victoria. 



[10 May, 1912. 



it contains easily available oxygen which is useful, while at the same time 

 it yields NH5 in the nascent state in the process of its reduction. This,, 

 however, is merely a suggestion; whatever the physiological reasons the 

 superiority of nitrate to ammonia nitrogen for direct crop production may 

 be taken as an established fact. 



It has been indicated that nitrification is the work of certain soil bac- 

 teria. There are two kinds of bacteria and two stages in the change, but 

 apparently both have very much the same requirements, save in the nature 

 of their nitrogenous food'. One kind changes ammonia into nitrite, the 

 second changes nitrite into nitrate. The conditions for growth of these 

 bacteria are therefore the conditions for nitrification. They require — 



1. The ordinary plant food of crops except iron. 



2. An available base to neutralize the acids produced — carbonate of 



lime being the best. 

 An ammonium salt — probably the carbonate. 

 Free aeration of the soil. 

 Sufficient moisture. 

 Darkness. 

 Temperature between 41 deg. and 130 deg. F., 97 deg. being; 



the best. 



I-'ILLIXG THE L'.Ol [ i_E. 



If moisture is necessary for nitrification, it follows that conservation of 

 soil moisture has a double purpose. The moisture is held in reserve for the 

 use of a future crop, but its presence meanwhile tends tO' the production of 

 nitrates. To find how far exactly, and within what limits the presence of 

 soil moisture has an effect upon the production of nitrates was the object 

 of these experiments. 



Method of Work. 



The method of investigation was as follows : — Air-drv soil equal to 300- 

 grams dry soil was placed in a bottle of 3 inches diameter, 6 inches high,. 



