CYANAMID — manufacture:, CHEJMISTRY AND USES 73 



cultural experience has shown that nitrogenous fertilizers are 

 not utilized as economically when applied alone as when they 

 are used in conjunction with phosphates and potash salts; the 

 presence of phosphorus and potassium seems to greatly modify 

 the ability of the plant to assimilate nitrogen. As a general 

 rule, it is seldom, indeed, that more than 25 pounds of nitro- 

 gen, derived from a single source, is applied at one time, 

 unaccompanied by phosphates and potash. In normal agri- 

 cultural practice, therefore, the question of toxicity of the 

 common nitrogenous fertilizers may be disregarded. If the 

 farmer wishes to depart from the normal practice, it is usually 

 best to follow the instructions issued by fertilizer manufac- 

 turers for the use of their products. Such instructions usually 

 designate 20 to 25 pounds of nitrogen per acre as the maximum 

 application, and recommend that the material be applied during 

 the preparation of the soil a week or more before the seed 

 is sown. They also caution against the danger of direct 

 contact of the undiluted fertilizer with the leaves or roots of 

 the plant. 



OTHER EXPLANATIONS OF TOXIC ACTION. 



Whether or not acetylene, which may be generated by the 

 action of moisture on a lime-nitrogen containing calcium car- 

 bide, is harmful to plant life, is of little interest to the 

 Cyanamid industry, since the material prepared for use as a 

 fertilizer does not contain calcium carbide. The lime-nitrogen 

 made in Europe in former years, sometimes contained slight 

 amounts of carbide but it is extremely doubtful if there were 

 any harmful effects from this ingredient. H. Kappen^ and 

 E. Haselhoff^ claim that they^ could observe no harmful effects 

 of acetylene on plant growth. No reports have been found 

 which show that acetylene may be harmful. 



The free lime in the German "kalkstickstoff" or lime- 

 nitrogen is in the form of calcium oxide, while in the Ameri- 



^ Fuhling's Landw. Zeit., Apr. 1908, 286. 

 » Landw. Vers, stat., 68, 1908, Nos. 3 and 4. 



