42 SOIL BACTEEIOLOGY 



Exercise 8 

 Effect of Depth on Rate of Ammonification 



1. A portion of the soil from Exercise 5, page 22, maybe 

 used for this study. 



2. Prepare sixteen tumblers with 50 grams of soil in 

 each tumbler. 



3. In order to prevent contamination of the soil the 

 tumblers and clover must be sterilized. 



4. Arrange thus: 



(a) I and 2, surface soil. 



3 and 4, surface soil plus i per cent, clover. 



(b) 5 and 6, i foot deep. 



7 and 8, i foot deep plus i per cent, clover. 



(c) 9 and 10, 2 feet deep. 



II and 12, 2 feet deep plus i per cent, clover. 



(d) 13 and 14, 4 feet deep. 



15 and 16, 4 feet deep plus i per cent, clover. 



5. After six days' incubation at 28° C. determine the 

 amount of ammonia. 



6. Tabulate. 



Table 13. — Effect of Depth on Rate of Ammoniflcaimn 



No. 



Position. 



Ammonia nitrogen in loo gm. of soil. 



Nitrogen 



Total. 



Blank 

 subtracted. 



Average. 



ammonified. 



I 

 2 



3 

 4 



S 

 6 



7 

 8 



Surface, 

 do. 



1 foot, 

 do. 



2 feet, 

 do. 



4 feet, 

 do. 



Mgm. 



Mgm. 



Mgm. 



Per cent. 



