BIOLOGICAL SOIL PROCESSES 



613 



Some further experiments were carried out with soil as a 

 medium. One hundred grams of soil were inoculated with 10 

 CO. of a 2 per cent solution of KNO3, and incubated twenty- 

 one days at 30°C. under aerobic and anaerobic conditions. 



With the greenhouse type of soil, denitrification took place, 

 to a greater extent under anaerobic than under aerobic condi- 

 tions. With the other two types of soil there was no loss of 

 nitrogen. It is evident that soil as a medium does not give 

 as good results as the solutions in regard to denitrification. 



In general, denitrification goes on under aerobic and anaerobic 

 conditions. An excess of air does not seriously inhibit the pro- 

 duction of nitrogen, although sHghtly less nitrogen is lost. The 

 process proceeds slightly better under anaerobic conditions, al- 

 though almost as much nitrogen is lost under aerobic conditions. 

 Denitrification proceeds better in solution than in soils, nitrogen 

 being lost only in the greenhouse type of soil and not in the 

 other two types. 



REFERENCES 



Brown, P. E. 1913 The effects of barnyard manure. Iowa Agr. Res. Bull. 

 13, 423^38. 



Haselhoff and Bredermann 1906 Investigation on Anaerobic Nitrogen-Col- 

 lecting Bacteria. Experiment Station Record 18, 429. 



HiBBARD, P. L. 1910 Notes on the determination of nitrogen by the Kjeldahl 

 method. Jour. Ind. and Eng. Chem., 2, 463. 



