BIOLOGICAL SOIL PROCESSES 



611 



H2O 1000.00 



KNO3 2.00 



MgS04 2.00 



Citric acid 5.00 



K2HPO4 2.00 



CaCl 0.20 



NaaCOs 4.25 



For the soil work, 100 grams of soil were inoculated with 0.2 

 gram of KNO3. Anaerobic conditions were again obtained with 

 sterile paraffin oil for the solution work, and by the absorption 

 of oxygen with pyrogallic acid and caustic soda for the soil work. 

 In the following experiment 200 cc. of Giltay and Aberson's 

 solution were inoculated with 2 grams of the soils of the three 

 types and then incubated for twenty-one days at 30° C. under 

 aerobic and anaerobic conditions. 



Experiment XIV. Denitrification in solution. Nitrogen in milligrams per WO 

 cc. of solution. 



Aerobic 



Denitrification seems to proceed better under anaerobic con- 

 ditions than under aerobic conditions. The difference is not 

 very marked, though noticeable. Again the process seems to 

 proceed best in the richest soil, probably due to the fact that 

 there are more bacteria of the denitrifying type present. 



In the following experiment washed air was bubbled through 

 200 cc. of the solution for twenty-one days at 30°C. 



