36 



SOIL BACTERIOLOGY 



8. Similar samples may be drawn after three or four 

 days and the amount of ammonia titrated. 



9. Tabulate the results. 



Table 9. — Ammonification of Urea. 







Ammonia nitrogen m too c c of solution. 



~ ' 



No 



Xpoculam 











After two days. 



After three days. 



I 



None. 



Total. 



Per cent. 



Total. 



Per cent. 





2 



do. 













3 

 4 

 5 



Soil. 



do. 



Manure. 













6 



do. 













Exercise 2 



Isolation of Urea-fermenting Organisms 



1. Inoculate duplicate tubes of urea solutions as follows: 



{a) Medium 19 soil. 



{h) Medium 19 manure. 



{c) Medium 20 soil. 



{d) Medium 20 manure. 



A small inoculum is suf&cient. In place of tubes {a) 

 and (&), cultures from the preceding exercise may be used. 



2. Two or three days after inoculation examine the test- 

 tube cultures for ammonia production (Nessler's reagent, 

 P- 135)- 



3. From one tube of each medium showing abundant 

 growth make transfers into tubes of sterile urea solution or 

 water blanks. A wide range of dilutions should be made. 



4. Pour plates from the different dilutions with the 

 same medium as in the tube culture plus gelatin (m. 23). 



