214 



Manuring for II<nf 



The. indirect evidence of marked diilerences in bacterial activity 

 on the different plots was fully borne out by direct determinations, 

 made in liUl, the results of which arc summarised in Table XI. 



Table XI. Bacterial Activity in Soils. 



* Colonies on Agar incubated 3 days at 38° C. 



f After 3 days' incubation (5 gms. soil). 



i „ 21 „ „ at 28° C. (5 gms. soil). 



§ „ 7 „ „ (5 gms. soil). 



II „ 3 liours' „ at 28° C. (5 gms. soil). 



It will l)e observed tiiat, with the exception of the production 

 of nitrates on Plot 7, tlie number and activity of the organisms were 

 relatively greater on the dunged plots than on the plots which were 

 either unmanured or received only "artificials." Further that bacterial 

 activity of all kinds was much greater on the nitrate plots (7, 9. 11) 

 than on the corresponding ammonia plots (8, 10, 12). The adverse 

 conditions for bacterial life on Plot 12 are strikingly exemplified. The 

 soils which showed the lowest bacterial activity (8, 10, 12) showed 

 also the lowest moisture-content and carried the biggest proportion 

 of dead undccayed grasses {cf. p. 213). 



The differences would appear to be least pronounced with regard 

 to the ammonia-producing organisms, but fvirther tests showed that 

 the data recorded in the table scarcely give a fair indication of the real 

 differences in ammonia-prodiu'ing power of the different plots. The 



