240 



Bacteriological Department. 



[Bull. 161 



TABLE XVI. 



Total nitrites, 1031; total ammonia, 34,278. 



NUMBER OF BACTERIA. 



Tables V to VIII show a great variation between the number 

 of bacteria at the beginning of the experiment and at the close. 

 This condition holds in all subplots in both sandy and silt 

 loam soils. This may be due to the lessening amount of food 

 available to the bacteria because the temperature, moisture 

 and air remain throughout the experiment within the limit of 

 experimental variation. 



Tables V to VIII show exceptionally high numbers of bac- 

 teria, sometimes in the surface six inches, and again at the 

 depth of twelve inches. The extra large numbers which are 

 found in some samples from the first six inches of soil were 

 nearly always attributable to manure or quantities of organic 

 matter, while. those in the subsoil were usually near some bur- 

 row, or at times were due to the presence of a heavy, decaying 

 root. 



