79 



siliop of pipcridine was considerably increased by 

 liming. From the foregoing it might be suggested tliat 

 a (lifTerent organism, or group of organisms, shoukl 1)C 

 involved in tiie deeom position of such compounds. 



Another interesting point which deserves mention is 

 the non-toxic action of vanillin toward the decomposi- 

 tion of pij)eridine. In vanillin treated soils nitrification 

 of dried blood and pyridine was seriously reduced, and 

 of quinoline, practically inhibited. But the decompo- 

 sition of pipcridine was about as great in the presence 

 of vanillin as in the untreated soils. There are several 

 possible explanations of these differences. The decom- 

 position of pipcridine may be caused by an organism, 

 or group of organisms, which are unaffected by va- 

 nillin; while the nitrification of quinoline, etc., may be 

 due to an organism or group of organisms to which va- 

 nillin is toxic. Again, vanillin may be toxic to the ni- 

 trification of pipcridine, quinoline and similar sub- 

 stances. But in presence of pipcridine, certain organ- 

 isms destro}'^ the vanillin, thereby permitting pipcridine 

 decomposition to proceed; while in the presence of 

 quinoline the action of the vanillin destroying organ- 

 ism or organisms is inhibited. In other owrds, there 

 might be a mutual inhibitation of the organisms re- 

 quisite to quinoline and vanillin decomposition. 



It is rather generally accepted that liming an acid 

 soil increases nitrification, and this view seems to be 

 correct for a large number of compounds. However, 

 quinoline and quanidine carbonate are two exceptions 

 to be noted among the compounds used in this work. 

 And it is conceivable that other basic nitrogenous com- 

 pounds may be nitrified best in acid soils. Again, the 

 fact that a substance inhibits the nitrification of one 

 com])ound is not proof that the compound inhibits 

 nitrification in general. For example, vanillin reduces 

 or even inhibits the nitrification of quinoline, while the 

 nitrification of pipcridine seems to be but little affected 

 by the addition of vanillin. Likewise, cumarin may 

 exert a decided inhibitory effect on the nitrification of 

 one compound and but little on another. Further, the 

 inhibitory action of a compound toward nitrification 

 may be quite different in different soils. In view of the 

 results here given, a general rule in regard to nitrifica- 

 tion would appear to be impossible. 



In most instances lime greatly reduced the toxicity 

 of pyrogallol, vanillin and cumarin, toward nitrifica- 



