278 



AZOF I CAT ION 



noted by Lipman. These soils were kept at the various moisture 

 contents for four months. All were then incubated at 28 C. for 

 twenty-one days with a moisture content of 20 per cent. 



Treatment. 

 Per cent. 



12.5 

 15.0 

 17.5 

 20.5 

 22.5 



Nitrogen fixed. 

 Per cent. 



100 

 108 

 102 

 104 

 108 



In this soil the optimum for the aerobes would appear to be at 

 17.5 per cent, and that for the anaerobes 22.5 per cent, or higher. 



90 100 



FIG. 34. Average percentages of ammonia 



and nitric nitrogen 



formed and nitrogen fixed in soil receiving varying quantities of water. On 



the ordinate is given the per cent, increase of the respective substances and on the 

 abscissa the quantity of water applied as per cent, of water-holding capacity. 



