CONDTTIONS FAVORING DENITHIFICATION. 39 



BXEKCISE XXIX. 



CONDITIONS FAVOKING DENITRIFICATION IN SOILS. EXCES- 

 SIVE MOISTURE AND EXCESSIVE ORGANIC MATTER. 



1. Weigh off twelve 100 gram portions of air-dry, sieved 

 f.oil, in tumblers. 



2. Add 0.5 gram ISTaKOg to each. 



3. Arrange thus : 



1 & 2 — nothing. 



3 & 4 — 20 grams of horse manure. 

 5 & 6 — 20 grams of dextrose. 

 7 & 8 — nothing. 



9 & 10 — 20 grams of horse manure. 

 11 & 12 — 20 grams of dextrose. 



4. Stir in these materials very thorouglily by means of a 

 sterile spatula. 



5. To each add 10 cc. of a soil infusion prepared by 

 shaking 100 grams of a fresh soil in 200 cc. of sterile water 

 for 5 minutes. 



6. Add sterile water to soil portions 1-6 to bring the 

 moisture content up to the optimum, or 50% saturation, 

 making such further additions where the horse manure and 

 dextrose are added that organic matter containing 70% 

 water shall be present. 



7. To soil portions 6-12 add sterile water to bring the 

 moisture content up to 100% saturation, making further 

 additions for the organic matter as before. 



8. Incubate 10-14 days at 20° C. 



