400 



Journal of AgriculiKrc, \ ictona. [lo July, 191 2. 



which had been air-dried, and stored at the laboratory for three months. 

 Two of those bottles marked A were put away dry on 23rd February, 

 while other two marked B were wetted to 60 per cent, of the saturation 

 capacity, and put away on the same day. After fifty days (13th April), 

 the contents of both A bottles were also wetted, and at the same time one 

 of A and one of B received o.i gram ammonia nitrogen as sulphate. The 

 bottles were again set aside, and after twenty-three days (6th May), the 

 progress of nitrification was determined with the following results: — * 



Table V. 



The soil was a poor one, and there v\as little difference in the unmanured 

 blanks. Where ammonia was given, nitrification, however, went on much 

 more quickly on the soil previously kept wet, showing that continued 

 existence in a dry soil impairs the vigour of the germs, but that under 

 moister conditions, they recover. This question does not affect the influence 

 of added substances, where the same soil is used throughout. What it 

 shows is that after a long dry spell, nitrifving activity will not im- 

 mediately revive with the rain because the organisms require some time 

 to recover their normal vigour. 



Summary. 



1. Mild lime is an effective means of promoting nitrification, and its 

 action begins at once. 



2. It is a safe dessing both as regards quantity and time of applica- 

 tion. 



3. Caustic lime requires greater caution in its use. 



4. It should not be applied too near the time of seeding. 



5. It should not be applied during the growth of any crop. 



6. It should be used in smaller quantities than mild lime. 



7. It will probably have a similar action to mild lime eventually. 



8. Magnesium carbonate in a limestone may or may not damage crops, 

 hut it appears to favour nitrification. 



9. Red and brown soils, other things being equal, favour nitrification, 

 as they contain a slow-acting liase in the form of iron rust. 



10. Gypsum is a slow form in which to apply lime. 

 Superphosphate may prove a useful aid to nitrification on some 



II 

 soils. 

 12 



13 



14 



Salt delays nitrification. 



Sour soils are verv unfavorable to nitrification. 



Ploughing in of green or fresh stable manure may cause a tempo- 

 rary shortage of nitrates, particularly on damp soil. 



15. The nitrifying organisms are weakened by continued drought, and 

 where the surface soil becomes unduly parched in a drv spell, nitrification 

 will begin slowly after rain comes. 



