106 AGRICULTURAL BACTERIOLOGY. 



CAN THE FARMER INCREASE NITRIFICATION ? 



From all this it follows that one of the primary conditions 

 for soil fertility is the presence of proper nitrifying bacteria in 

 the soil, and proper conditions for their growth. To the agri- 

 culturists it has thus become a practical question to learn how 

 these bacteria, if not already present, may be added to the 

 soil, and how they may be stimulated into activity, if they are 

 present but inactive. To the solution of these questions bac- 

 teriologists are strenuously applying themselves, and, although 

 they have not answered all of the questions arising, some 

 facts of significance have already been settled. 



In the first place, the cultivation of the bacteria in the labora- 

 tory and the inoculating of pure cultures into the soil appears 

 hardly practical. The organisms are too difficult of cultivation 

 to promise practical results along this line of work. More- 

 over this is not necessary. Most soils seem to have the 

 nitrifying bacteria already present, so that a stimulation of 

 their action is needed rather than the addition of more bacteria 

 of the same kind. Further, if it is necessary to supply the 

 soil with the nitrifying bacteria, this can readily be done by the 

 use of manure, which contains them in abundance, and this 

 process is certainly cheaper and probably more efficient than 

 the preparation and use of pure cultures. 



It is of more importance therefore, to determine how the 

 growth of the nitrifying bacteria can be stimulated into activity. 

 This can only be determined by studying the conditions under 

 which they most readily grow and applying them in practice. 

 In this connection it has been learned that a certain amount of 

 moisture is necessary for their proper action, wet soil showing 

 more nitrification than soil that is simply damp or saturated 

 with water. The process of nitrification takes place only when 

 the temperature is more than 5 above freezing, and is more 

 vigorous with a rise in temperature. Hence it ceases in the 

 winter months and is most vigorous in the summer. The ac- 



