54 SOIL BACTERIOLOGY 



Exercise i8 

 Effect of Limestone on Nitrification 



1. Prepare ten tumblers of soil, loo grams in each- 

 Two types of soil may be used, neutral and acid. 



2. Arrange each soil type as follows: 



(a) I and 2, untreated. 



(J)) 3 and 4, 30 mgm. of nitrogen as ammonium sulphate, 



(c) 5 and 6, 30 mgm. of nitrogen as ammonium sulphate plus i gram 



CaCOa. 



(d) 7 and 8, 30 mgm of nitrogen as gelatin. 



(c) 9 and 10, 30 mgm of nitrogen as gelatin plus i gram CaCOs 



3. Stir in the chemicals thoroughly by means of a sterile 

 spatula. 



4. Add water and incubate for ten to twenty days at 

 room temperature. From time to time replace the water 

 lost by evaporation. 



5. At the end of the period of incubation analyze for 

 nitrates. 



Table 23 — Effect of Limestone on Nttrification 







Nitrate nitrogen m 100 gm of soil 





No. 



Treatment. 





Nitrified. 



Total 



Blank 

 subtracted 



Average 

 Mgm. 





Per cent. 



Mgm 



Mgm 



Per cent 



I 



None. 











2 



do. 











3 



Ammonium sulphate. 











4 



do. 











5 



Ammonium sulphate 

 plus I limestone. 











6 



do. 











7 



Gelatin. 











8 



do. 











9 



Gelatin plus 1 lime- 

 stone. 











10 



do. 











