472 SOILS: PBOPSBTISS AND MANAGEMENT 



Some typical results of investigations by Russell and 

 Hutchinson on the effect of partial sterilization on bac- 

 teria numbers, ammonia production, and presence of 

 protozoa are given below : — 







Nitrogen 









Bacteria 



AS NHsAND 









AFTER Sixty- 



NO3 AFTER 



Detri- 



Protozoa 

 Found 





eight Days, 



Sixty-eight 



mental 





TO a Gram or 



Days, Parts 



Factor 





Dry Soil 



TO A Million 

 or Dry Soil 















f Ciliates 



Untreated soil . . 



11,100,000 



13.0 



Present 



I AmcBba 

 [Monads 



Soil heated to 40° C.l 

 for three hours J 



7,500,000 



14.4 



Present 



f Ciliates 

 < Amoeba 

 [Monads 



Soil heated to 56° C.j 

 for three hours j 



37,500,000 



36.7 



Killed 



M] MUed 



390. Greig-Smith's theory. — An entirely different 

 explanation of the effect of partial sterilizatL on soils 

 has been advanced by Greig-Smitli.^ He states that 

 when disinfectants are appHed to the soil their action is 

 a double one. They kill the less resistant bacteria, and 

 dissolve from the surfaces of the soil particles a waxy 

 covering, to which he has given the name " agricere." 

 The surviving bacteria, among which are the beneficial 

 ones, are able to develop more rapidly because of the 

 greater accessibility of the food supply which the re. 

 moval of the " agricere '' has exposed. 



Greig-Smith holds that heat destroys substances toxic 



1 Greig-Bmitli, R. The Baeteriotoxins and the "Agricere" 

 of Soils. Centrlb. f. Bakt., II, Band 30, Seite 154-156. 1911. 



