8o CYANAMID — MANUFACTURE, CHEMISTRY AND USES 



not exceed lo pounds per acre. Hence, the above quantities 

 are many times larger than any met in agricultural practice. 



A similar experiment was made in pots containing 8 kg. of 

 soil, manured with double superphosphate, potassium sulphate 

 and nitrogen at the rate of 120 pounds of PoOj, K2O and N per 

 acre respectively. The lime-nitrogen contained 11.8 per cent. 

 N and the dicyandiamide 59.9 per cent .N. The yields in grams 

 of air-dry plants were as follows : 



Fertilized days before planting 



Fertilized with o 7 14 21 



Ammonium sulphate .. . 67.5 — — — 



Lime-nitrogen 65.6 69.6 70.6 74.8 



Dicyandiamide 66.6 74.3 73.8 71.5 



The yields of grain were : 



Fertilized days before planting 



Fertilized with o 7 14 21 



Ammonium sulphate • • . 29.5 — — — 



Lime-nitrogen 28.3 30.0 29.5 33.2 



Dicyandiamide 30.5 33.5 31.7 33.7 



In this experiment the highest results were obtained with 

 dicyandiamide applied a week before planting. When applied 

 at the time of planting the results are about the same as those 

 with ammonium sulphate. 



PURE SUBSTANCES AND TOXICITY. 



There are several observations reported in the literature that 

 may help us to understand why a chemically pure dicyandia- 

 mide should be toxic, while an impure dicyandiamide may have 

 a fertilizing value equal to that of ammonium sulphate. 



It has been noted by Sabaschnikoff^ that a fertilization with 

 chemically pure calcium cyanamide, in comparison with lime- 

 nitrogen containing the same amount of nitrogen, gives only 

 from one-third to one-half as large an increase in yield as is 

 obtained from the lime-nitrogen, both being applied under 

 exactly the same conditions. 



C. J. Milo^ made some experiments on sugar cane, in which 



1 Mitt. Landw. Inst., Univ. Leipzig, Vol. IX 1908, p. 106. 



2 Archief voor de Suikerindustrie in Nederlandsch-Indie, 20, 482-539. 



