SOIL BACTERIOLOGY 



4. Bring the moisture content of the soil to two-thirds 

 saturation. 



Note. In order to secure the proper moisture content it is necessary to 

 take into account the water-holding capacity of the added substances, e. #., 

 i gram of casein or blood-meal requires about 2 c.c. of water; i gram of 

 clover, about 5 c.c. of water. 



Allow the soil to stand for one hour or more and remix 

 with a sterile spatula. 



5. Determine the amount of ammonia nitrogen in samples 

 !> 2 > 5) 6) 9) and 10 at once. The ammonia nitrogen of 

 these cultures or controls is to be subtracted from the am- 

 monia nitrogen found at the final analysis. This gives the 

 figures "blank substracted." 



6. Cover the remaining tumblers with Petri dishes and 

 incubate for four to six days at 28 C. Now determine the 

 ammonia content of all of the soils. The percentage of 

 nitrogen in the different substances is given on the label. 



7. Tabulate results. 



TABLE n. Ammonification of Various Substances 



