60 SOIL BACTERIOLOGY 



10. Tabulate results. 



TABLE 25. Denitrification in Soil 



Exercise 25 

 Autotrophic Denitrifying Bacteria 



1. Prepare six tall tubes of Lieske's culture-medium 

 (m. 38). The tubes for this exercise should be at least 

 10 to 15 inches long and filled four-fifths full of the 

 culture-medium . 



2. Inoculate: 



(a) i and 2, uninoculated. 



(&) 3 and 4, i gram of garden soil. 



(c) 5 and 6, i c.c. of sewage. 



3. Incubate the cultures for six to eight weeks at 28 0: t3^ 



4. Determine the total nitrate content of the different 

 cultures. 



