6o6 



Journal of Agricultural Research 



Vol. XV. No. n 



Table III. — Effect of carbon disulphid upon nitrogen fixation and nitrate accumulation 



a Nitrates in milligrams per 100 gm. of soil. 



6 Nitrogen fixed in milligrams per 50 cc. of culture. 



c Milligrams. 



EFFECT OF MOISTURE CONTENT OF SOIL UPON THE GERMICIDAL 

 ACTION OF CARBON DISULPHID AND TOLUOL 



The results obtained from the two sets of experiments given above 

 were so radically different that it seemed necessary to ascertain, if pos- 

 sible, the cause of the differences. The soil, while not the same, was 

 quite similar and it did not seem possible that such wide differences in 

 the effect of the reagents could be due to differences in the character of 

 the soil. An examination of the conditions under which the two sets 

 of experiments were conducted revealed only one important difference. 

 The moistuie content of the soil in the first experiments was 13 percent, 

 while in the second set the moisture content was only 4 per cent. Experi- 

 ments were therefore planned to throw some light upon the influence of 

 the moisture content of soil on the effectiveness of carbon disulphid 

 and toluol in killing Azotobacter. 



In these experiments the same soil was employed as in the second set. 

 Three conditions of the soil with respect to moisture were compared. In 

 the first the water content was 3 per cent, in the second 10 per cent, and 

 in the third 20 per cent. The soil was made up to different moisture 

 contents before treatment. 



After the chemical was allowed to act for three days all samples were 

 cultured for Azotobacter. The bottles were then opened and left open 



