6i4 Journal of Agricultural Research voi. xv.no. n 



content used in our experiments. The high-moisture content, accord- 

 ing to Kelley, would prevent carbon disulphid and toluol from coming 

 in contact with the organisms. The results herein reported appear 

 to show that this is not true. 



A study of the literature devoted to the question of partial steriliza- 

 tion by means of volatile antiseptics reveals a mass of conflicting data 

 and numerous contradictions and criticisms. As far as ascertained, 

 the influence of moisture upon such treatment has been considered by 

 only one investigator. Greig-Smith ^ found that the effct of toluol upon 

 soil protozoa varied with moisture content. The available review of 

 this paper gives no data except the statement that 20 per cent of toluol 

 failed to destroy certain protozoa if the moisture content were less than 

 one-tenth saturation, but if the moisture content was above this i or 2 

 per cent of toluol was sufficient to kill them. In the soils used any 

 degree of saturation below oije-tenth would approach very closely an 

 air-dry condition. It appears, then, that the experiments reported in 

 this paper agree in general with Greig-Smith 's. It is possible that 

 many of the conflicting results heretofore reported as to the effect of 

 volatile antiseptics, or so-called partial sterilization, may be explained 

 solely upon the moisture content of soil when such treatment was made. 



SUMMARY 



Carbon disulphid and toluol when applied to soils in sufficient quanti- 

 ties will destroy Azotobacter group of organisms and check the accumu- 

 lation of nitrate nitrogen and possibly will destroy the nitrif5dng organ- 

 isms. 



The quantities necessary to produce such effects vary quite widely 

 depending among other things upon the quantity of moisture present. 



Apparently if the quantity of carbon disulphid or toluol is sufficient 

 to have any effect upon Azotobacter they are usually completely 

 destroyed. On the other hand, there is a great difference in the quan- 

 tity necessary to destroy nitrifying organisms and that necessary to 

 check their activity. 



There are nitrogen-fixing organisms other than Azotobacter present 

 in soils which are not destroyed with 10 cc. of carbon disulphid or 

 toluol even when the moisture content of the soil is high. 



Following treatment with carbon disulphid and toluol there is no 

 appreciable accumulation of ammonia unless nitrification has been 

 checked. 



There is no evidence in these experiments to show that treatment 

 with antiseptics stimulates the nitrifying organisms, and there is little 

 evidence to indicate a stimulative effect upon the ammonifying or 

 nitrogen-fixing organisms. 



' Greig-Smith, R. the action op toluene upon soil protozoa. (Abstract.) In Nature [London], 

 V. 94, no. 2360, p. 581. 1915. 



