a. A. CowiE 127 



Summary. 



Cyanamide readily breaks down in the soil yielding ammonia, which 

 then nitrifies in the usual way. The conversion of cyanamide nitrogen 

 into nitrate is practically quantitative, and its efltectiveness as a fertiliser 

 is approximately equal to that of ammonium sulphate. 



Dicyanodiamide has given no evidence of nitrification in the soil 

 even after several months. On the contrary, it is actually to.xic to 

 plants, although in small amounts it causes no appreciable injury. It 

 does not affect germination at any of the concentrations used. 



Dicyanodiamide is also toxic to the nitrifying organisms and stops 

 the normal oxidation of ammonia in soils containing ammonium sulphate. 

 It likewise inhibits the transformation into nitrate of the ammonia 

 produced from cyanamide in the soil and causes an accumulation of 

 ammonia under these conditions. It does not sensibly retard the 

 formation of ammonia from cyanamide. 



Dicyanodiamide does not appear to affect so drastically the other 

 organisms of the soil, especially those concerned in the decomposition 

 of protein. It exerts little influence upon the numbers developing on 

 gelatine plates or the rate and extent of the decomposition of dried 

 blood. 



In conclusion the writer desires to acknowledge his indebtedness to 

 Dr E. J. Russell, who kindly suggested the lines of the investigation, 

 for his helpful advice throughout its progress, to Dr W. E. Brenchley, 

 for much valuable assistance in connection with the pot-culture experi- 

 ments, and also to Mr B. F. Davis, F.I.C., who kindly supplied samples 

 of the various products and made many useful suggestions in the 

 course of the work. 



