224 Bacteriological Department. [Bull. 161 



the usual way by using the common sugar bouillon media in 

 fermentation tubes, each of which were inoculated with two 

 cubic centimeters of soil suspension. 



Reduction of Nitrates to Nitrites. The denitrifying prop- 

 erties, or reduction of nitrates to nitrites, were determined by 

 inoculating with 2 cubic centimeters of soil suspension, 10 cubic 

 centimeters of Witte's peptone medium, which contained 0.2 

 gram of potassium nitrate per 1000 cubic centimeters. The 

 tubes were allowed to stand for five days and then tested for 

 nitrites by the addition of sulfanilic acid and naphthylamine 

 chlorid. The results were compared with a standard and re- 

 corded as so many parts of nitrites per million. 



Temperature. In the preliminary work the temperature was 

 recorded for the surface foot, but commencing with July 6, 

 the temperature was recorded for each successive second inch 

 up to one foot, or for each soil sample taken. 



Acidity of Soil. At the beginning of the experiment the 

 soil showed acid to litmus at the end of thirty minutes, while 

 at the end of the experiment it showed acid to litmus at the 

 end of ten minutes. 



Field Notes. The condition of the soil surface, the time 

 which had elapsed since the last rain, the amount of precipita- 

 tion, and other factors such as masses of undecomposed or- 

 ganic matter, plowed soil, unstirred subsoil and burrows or 

 heavy roots were recorded when samples were taken. 



Mechanical Analyses. A mechanical analysis was made of 

 each of the two plots of soil under observation. The results of 

 these analyses were as follows : 



SILT SOIL, PLOT B. 



Humus 3.15 per cent. 



Volatiles 4.86 



Fine gravel 00 



Coarse sand 20 



Medium sand 26 



Fine sand .46 



Very fine sand 24.16 



Silt 38.91 



Clay 28.00 



Total 100.00 per cent. 



