NITRIFICATION OF VARIOUS SUBSTANCES 5! 



* 



2. Treat as follows: 



(a) i and 2, untreated. 



(b) 3 and 4, 30 mgm. of nitrogen from (NH 4 ) 2 SO 4 . 



(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 



