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virgin soil in 28 of the 44 pairs such was the case and to the long period 

 through which the tests ran allowing the slower action of the virgin soils to 

 finally approach that of the cultivated ones. In 15 of the 19 pairs in which 

 the virgin excelled the cultivated sample in nitrate accumulation, the organic 

 nitrogen was higher in the virgin soil. 



In yet another particular the present tests failed to confirm those with 

 ammonium sulphate in the accumulation of nitrates as regards soil type. 

 On the basis of the classification previously used, averages from a number 

 of soils of the same general type are given in Table VII. 



TABLE VII. Nitrate Accumulation of a Number of Virgin Soils of 



Various Textures. 



The contradiction is in the case of the clay loams registering highest in 

 nitrifying power with ammonium sulphate and lowest in nitrate accumulat- 

 ing power. The other results are in accord with those previously cited. It 

 is difficult to explain such a discrepancy as this. Of course the validity of 

 any comparison of the two series of tests is open to question an inorganic 

 nitrogen supply being used in the one case and an organic in the other, and 

 the duration of the two experiments so widely different. Yet whatever cor- 

 relation is obtained serves to strengthen the conclusions from each test. 

 Nitrification at best is a process which is notorious for discrepancies even 

 under ideal conditions for measuring it, and agreements which come about 

 despite inequalities in methods are not unwelcome. The failure of clay loam 

 to accumulate quantities of nitrate which correspond to their power of 

 nitrifying ammonium sulphate belongs to that phase of nitrification which 

 the authors would not attempt to explain. 



Attention is to be called to the complete failure of certain soils to exhibit 

 nitrification. In the tests with ammonium sulphate, 10 virgin and 4 cul- 

 tivated soils exhibited this deficiency and 6 virgin and 5 cultivated soils 

 failed to accumulate any nitrates through the conversion of their organic 

 nitrogen. In Table I such soils are indicated by blanks in the columns con- 

 taining the quantities of nitrates. 



It is noteworthy that in most cases where the failure occurs it is true of 

 "both the virgin and cultivated soils of a pair. This quality of soils has often 



