AMMONIFICATION IN SOILS. 11 



EXEECISE V. 



AilMONIFICATION IN SOILS. 



1. AVeigli off in tumblers six 100 gram portions of air- 

 dry, sieved samples of the soil to be tested. 



2. Arrange thus: 



1 & 2 — nothing. 



3 & 4 — 5 grams of dried blood. 



5 & 6 — 5 grams of cottonseed meal. 



3. Stir in these materials very thoroughly by means of a 

 sterile spatula. 



4. Prepare an infusion of the soil by shaking 100 grams 

 of a fresh sample with 200 cc. of sterile water for 5- minutes. 



5. By means of sterile pipettes inoculate each of the six 

 portions of soil with 10 cc. of this infusion. 



6. Add sterile water to bring the moisture content up to 

 the optimum for the soil, using 12 cc. additional for those 

 portions containing the dried blood and cottonseed meal. 



7. Cover with Petri dish covers and incubate for 7-8 

 days at 20° C. 



8. Then transfer the soil to copper flasks, using about 250 

 cc. of water. Add 10-15 grams of MgO and a piece of 

 paralBn and distil off the ammonia present, collecting it in 

 standard acid and titrating against standard alkali. 



