SOIL BACTERIOLOGY 



Exercise 16 

 Effect of Soil Type on Nitrification 



1. Weigh out four loo-gram portions of garden soil, 

 field soil, and acid soil into clean, dry tumblers. 



2. In one-half of the tumblers mix thoroughly with the 

 soil i per cent, of clover tissue. 



3. Arrange as follows: 



(a) i and 2, garden soil untreated. 



(6) 3 and 4, garden soil plus i per cent, clover. 



(c) 5 and 6, field soil untreated. 



(d) 7 and 8, field soil plus i per cent, clover. 



(e) 9 and 10, acid soil untreated. 



(/) ii and 12, acid soil plus i per cent, clover. 



4. Add moisture until the soil is two-thirds saturated, 

 allow it to stand for one hour, and remix. 



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



6. After three weeks determine the nitrate nitrogen 

 (see p. 143) in numbers i, 3, 5, 7, 9, and n; after 6 weeks 

 in numbers 2, 4, 6, 8, 10, and 12. 



TABLE 21. Effect of Soil Type on Nitrification 



