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ROYAL SOCIETY OF CANADA 



to bring about in the soil the conversion of the compounds under in- 

 vestigation into inocuous forms. And in this connection it may be 

 remarked that even if these substances possessed no toxic action on 

 vegetable life their nitrogen would not be available for plant nutrition 

 until they had undergone nitrification, since practically it is only as 

 nitrates that ordinary farm crops obtain their nitrogen from the soil. 



The experiments conducted to ascertain the rate of nitrification 

 were carried on in pots holding five pounds of soil each. The soil 

 throughout the series was uniform and the estimations of the free 

 ammonia and nitrates were made at stated intentais after the applica- 

 tion of the cyanamide. Two pots were used as checks, and to these no 

 cyanamide was added, but their ammonia and nitrates were determined 

 on the same dates as those upon which the rest of the series were exam- 

 ined, so that changes normally taking place in the soil nitrogen could 

 be followed. The methods used for the determination of the nitrogen 

 compounds were those commonly employed in water analysis and con- 

 sequently the results may be considered as closely approximating the 

 truth. Throughout the period of trial the soil in all the pots was kept 

 under uniform conditions as regards moisture and warmth. The tem- 

 perature of the room in which the pots were kept ranged from 65° F. 

 to 75° F. 



Experiment I. — This consisted of four pots each containing an 

 amount of the calcium compound (37.84^ nitrogen) equivalent to an 

 application of 22.5 lbs. per acre of a compound containing 16<^ nitrogen. 

 The experiment was begun on 22nd October, 1904, and estimations 

 made on December 12th, 1904, and 21st March, 1905. 



With small applications, as in this experiment, the conversion of 

 the nitrogen of the cyanamide compound into ammonia proceeds fairly 

 rapidly; the second and third stages, by which the ammonium salts are 

 converted into nitrites and nitrates, are apparently of much longer 



