216 NITROGENOUS FERTILIZERS 



by plants it must be nitrified and this process takes place 

 in five stages as follows: 



First, hydrolysis to cyanamide and calcium hydroxide, 

 helped probably by the adsorptive processes in the soil, thus : 



CaCN 2 + 2H 2 = H2CN2 + Ca(OH) 2 . 



The calcium hydroxide is changed rapidly to carbonate. 



Second, the hydrolysis of cyanamide with the aid of 

 colloidal catalysts to urea, thus: 



H2CN2+ H2O = CO(NH 2 ) 2 . 



Third, the bacterial hydrolysis, or ordinary ammonifying 

 process, to ammonium carbonate, thus: 



CO(NH 2 )2+2H 2 0= (NH 4 )2C0 3 . 



Fourth, nitrification to nitrous acid and nitrites. 



Fifth, further nitrification to nitric acid and nitrates. 



Cyanamid is ranked as a fairly quick acting fertilizer, 

 about as good as ammonium sulphate. 



(c) Effect on the Soil. — Cyanamid while producing 

 nitric acid also carries considerably more calcium oxide than 

 is necessary to neutralize this acid. The residual effect is 

 like that of basic calcium nitrate, and is beneficial. Cases 

 have been reported where cyanamid has harmed crops, but 

 under ordinary farming conditions no danger from it need 

 be feared. 



161. Dried Blood. — By evaporating, drying, and grinding 

 animal blood from slaughter houses there is obtained a 

 product known as dried blood which is one of the best 

 organic nitrogenous fertilizers. It comes on the market in 

 two forms, red and black, the color depending on the processes 

 of manufacture. Red dried blood is the better of the two, 

 being more uniform in composition, containing more nitrogen 

 and being more available as a fertilizer. Its nitrogen content 

 is approximately 13 per cent. Black dried blood is not so 

 pure, being often mixed with hair, dirt, and other substances 

 which impair its value. Its nitrogen content varies greatly, 



