80 



tion. The beneficial results obtained with lime may 

 be due to the neutralization of soil acidity, thereby 

 increasing bacterial activity, or the lime may reacts 

 directly or indirectly, with these compounds, the result- 

 ant products being less injurious than the original. 



In several instances, greater nitrification was found 

 in the lime-pyrogallol series and the nme-vanillin 

 series than in the lime series alone. It may be possible 

 to explain these rather peculiar results, in the light of 

 recent work l)y Doryland and by Robbins. The results 

 obtained by Doryland (4) tend to show that while a 

 large amount of energy-producing material may give 

 rise to such large numbers of bacteria that the ammonia 

 produced from a nitrifiable substance may be entirely 

 consumed by the bacteria, a small amount of energy- 

 producing material may actually increase ammonia 

 accumulation. The explanation offered is that the 

 small amount of energy-producing material induces 

 large numbers of bacteria in the medium. When this 

 small amount of energy-producing material is exhaust- 

 ed the nitrogenous compounds remaining are attacked 

 as a source of energy, causing rapid ammonification 

 and ammonia accumulation. Robbins (8) has shown 

 that the addition of cumarin or vanillin to soil enor- 

 mously increases the number of bacteria present. He 

 has shown, further, that certain bacteria are able to 

 use these compounds as sources of energy'. It may be 

 possible, therefore, to explain the increased nitrifi- 

 cation in the presence of vanillin as being due to the 

 increased numbers of bacteria induced by the small 

 amounts of vanillin added. The vanillin in this case 

 producing effects similar to those found by Doryland, 

 where small amounts of energy-producing material 

 like dextrose caused increased ammonia accumulation. 



Summary 



(1) With the exception of naphthylamine, each of 

 the compounds used in this study was nitrified in soil. 



(2) At the concentration used, naphthylamine in- 

 hibited nitrification in both limed and unlimed soil. 



(3) Quinoline was nitrified most readily in soil 

 having the highest lime requirement. Lime retarded 

 or even inhibited nitrification of quinoline. 



(4) Lime practically inhibited nitrification of guan- 

 idiiie carbonate. Nitrification of dried blood, pipcri- 

 dine, nucleic acid, alloxan, and asparagine, was greatly 

 increased by lime. 



