414 



THE PRINCIPLES OF SOIL MANAGEMENT 



medium containing organic matter. This property 

 for a long time prevented the isolation and identifi- 

 cation of these organisms, as it was hardly conceivable 

 that organisms living in the dark, where energy can- 

 not be obtained from sunlight, could exist without 

 using the energy stored by organic matter. It has 

 been suggested, in explanation of this, that the energy 



OCTOBER 



Fig. 112. Curves showing the relation of the moisture and temperature of 

 the soil to the formation of nitrates which are given in parts per million of dry 

 soil. Depth of sampling, eight inches. These curves bring out clearly the fact 

 that the warmer soil temperature, combined with a moderately high soil mois- 

 ture content favors the formation of nitrates. 



produced by the oxidation involved in the process 

 of nitrification makes possible the growth of the or- 

 ganisms under these, apparently impossible, condi- 

 tions. Some experimenters report having grown 

 nitrobacteria in organic media, but it is generally 

 believed, at present, that this is not possible, and that 

 there has been some error in their work. 



The presence of peptone in the proportion of 500 

 parts per million completely prevents the develop- 



