NITRIFICATION OF VARIOUS SUBSTANCES SI 



2. Treat as follows: 



(a) I and 2, untreated. 



(b) 3 and 4, 30 mgm. of nitrogen from (NH4)2S04. 



(c) 5 and 6, 30 mgm. of nitrogen from casein. 



The proper amount of nitrogen is most conveniently 

 added from solution. Prepare a stock solution in such a 

 way that 5 c.c. equals 30 milligrams of nitrogen in the form 

 of casein or ammonium sulphate. 



3. Mix these substances thoroughly with the soil. 



4. Add sterile water to make half-saturation. 



5. Cover with Petri dishes and incubate at 28^ C. 



6. Weigh each week and restore loss of water by evap- 

 oration. 



7. Analyze for nitrate nitrogen after ten and twenty 

 days. 



8. Express the results in terms of milligrams of nitrate 

 nitrogen in 100 grams of soil; also as percentages of the 

 original substance nitrified. 



9. Tabulate results as follows: 



Table 20. — Nitrification of Various Substances 





Treatment. 



Nitrate nitrogen in 100 gm. of soil 





No. 



After ten days. 



After twenty days. 



Nitrified. 





Total. 



Blank 

 subtracted. 



Total. 



Blank 

 subtracted. 





I 



2 



3' 



Mgm. 

 None. 

 30 N. from 



(NH4)2S04 



30 N. from 

 casein. 



Mgm. 



Mgm. 



Mgm. 



Mgm. 



Per cent. 



