77- 



trates was recovered from each treatment except giian- 

 icliiie carbonate; the amount recovered from tlic soil 

 treated with dried blood and piperidine averaged 100 

 and 112 parts per million of soil, respectively. The 

 great corrective elfect that lime may exert in soil is 

 very strikingly shown by the results set forth above. 



Influence of Lime, Carbon Black, and Pyrogallol on 



Nitrification of Dried Blood in Presence of V.\nillin 



CuMARiN, and Diiiydroxystearic Acid. 



It has been shown that the toxicity of soil extracts 

 may be partially or even completely removed by the 

 use of such compounds as carbon black, pj'^rogallol or 

 lime. It was thought probable, therefore, that these 

 compounds might have a beneficial effect on nitrifica- 

 tion in soil to which toxic compounds were added. To 

 test this, a number of tumblers were prepared in the 

 usual way, and treated as shown in table VII. 



From each of the comparisons which may be made 

 with this data, it is seen that pyrogallol exhibited an 

 inhibitory effect on nitrification. 



Lime had a beneficial effect on nitrification under 

 each of the conditions in which it was used. This 

 result was to be expected from the numerous instances 

 given ill which the action of lime was shown to be 

 helpful. 



Table VII. — The Effect of Lime, Pyrogallol and Carbon 



Black on Nitrification of Dried Blood in Presence 



of Vanillin, Cumarin, and Diiiydroxystearic Acid. 



Nitrates Expressed as p. p.m. of Dry Soil. 



