78 ROYAL SO OIE! Y OF CANADA 



The decrease in the percentage of nitrogen converted into available 

 forms, as recorded in the last column of tables III and IV, is apparent 

 rather than real. It arises from the fact that there was a large and 

 apparently nnexplainable falling off in the available nitrogen in the 

 check pots, the differences in which from time to time were necessarily 

 used in the calculations to arrive at the conversion of the nitrogen of 

 the cyanamide compound apart from that of the soil proper. 



It would seem from a consideration of the data of this research 

 that with the increase in the amount of the cyanamide compound there 

 is a concomitant decrease in the rate of nitrification. This is probably 

 due, as already indicated, to a toxic action upon the nitrifying organisms 

 by the cyanamide compound, which action would naturally be increased 

 the larger the application. On the other hand, it may in part be due 

 to denitrifying changes leading to the loss of nitrogen in the free state. 



The conversion of the nitrogen of the cyanamide into available 

 forms is most probably, under favourable conditions, continuous, though 

 not uniformly so. The first stage may be considered possibly as purely 

 chemical, since water at ordinary temperatures converts the nitrogen 

 of cyanamide into ammonia. The further changes being brought about 

 through the agency of living organisms are necessarily slower and will 

 be regulated by many factors, prominent among which, as we have ob- 

 served, is the proportion of the cyanamide compound present in the soil. 



