INFLUENCE OF SOIL ON BACTERIA 201 



rapid increase which may persist for even 200 days or longer. 

 There is a tendency for ammonia to accumulate, thus showing 

 that it is either being produced more rapidly than it was before 

 the soil was heated or that something has happened so that the 

 ammonia is not as rapidly transformed into nitrates. After a 

 time the soil regains its power to produce nitrates, after which 

 they are produced in greater quantities than they were before the 

 soil was heated. 



The heating of a soil greatly accelerates the oxidation going 

 on within it, as may be seen from the following results reported 

 by Darbishire and Russell: 



Kind 0/ Soil 



Treatment 



Mgm. of Oxygen Absorhd in 



3 Days 



6 Bays 



p Days 



Hop garden soil 

 Hop garden soil 

 Garden soil 

 Garden soil 



untreated 

 heated to 95° C. 

 untreated 

 heated to 95" C. 



3-7 

 6.0 



I'S 

 10.9 



5-2 



8.2 



10.2 



27.2 



7.0 

 12.0 



15.5 



33''^ 



There is also an increase in the nitrogen-iixing powers of the 

 soil, as may be seen from the following results. They were ob- 

 tained with a soil which had been heated long enough to destroy 

 all life and then treated with extracts from a fertile soil. This 

 had been heated to varying temperatures. 



Temperature to Which Soil Extract 

 Was Heated H" C.) 



Mgm. of Nitrogen Fixed 



Not heated 



5.1 1 



50 



9.00 



SS 



14.14 



60 



16.38 



65 



14.42 



70 



13.02 



75 



^'^'3S 



80 



12.66 



85 



1Q.36 



