THE OXYGEN REQUIREMENTS OF BIOLOGICAL SOIL 



PROCESSES^ 



T. J. MURRAY 

 Deparlment of Plant Pathology and Bacteriology, Virginia Polytechnic Institute, 



Blacksburg, Virginia 



Received for publication, June 12, 1916 



The aim of this work was to find out whether the fundamental 

 processes carried on by soil bacteria proceed better under aerobic 

 or anaerobic conditions. 



The work was carried out with three soils, first a greenhouse 

 loam soil, rich in organic matter, second a field soil from the 

 experiment station plats, — a Hagerstown silt loam, and third, a 

 clay soil — a Hagerstown clay taken from the side of a hill slop- 

 ing down to a brook. These were selected to represent three 

 different types of soil and to secure different flora and different 

 conditions of microbic development. 



The biological processes in soil are influenced according to 

 Lipman (1911) by moisture, temperature, aeration, reaction, and 

 food supply. It seems to the writer that the relation of oxygen 

 to the fundamental soil processes has not been thoroughly in- 

 vestigated; and that it has not been fully established — taking 

 soil or synthetic solutions as media — whether nitrogen fixation, 

 nitrification, ammonification and denitrification will go on under 

 aerobic or anaerobic conditions only, and whether these processes 

 will take place better in the presence or in the absence of air. 



Preliminary experiments showed that ammonification, deni- 

 trification, and nitrogen fixation took place readily with or with- 

 out air. Nitrification on the other hand would not take place 

 under anaerobic conditions, either in soils or in solution in the 

 preliminary or subsequent experiments. The results of the work 

 on nitrification are therefore not included in this paper. 



1 Paper No. 45 from the Laboratories of Plant Pathology and Bacteriology, 

 Va. Agr. Exp. Sta. 



597 



