COMMERCIAL FERTILIZERS 505 



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



urea ammonium 



carbonate 



This may be converted into nitrates in the usual manner. 



426. The use of cyanamid. — The changes as here 

 described are those that proceed under favorable condi- 

 tions in the soil. When conditions are not favorable — 

 as, for example, when a soil is saturated with water or 

 when it is acid — some more or less injurious products 

 may be formed. For this reason cyanamid is not likely 

 to be so satisfactory on soils of this nature as on better 

 soils. To very sandy soils it is not well suited. Ordi- 

 narily its fertilizing value is not greatly below that of 

 sodium nitrate, and is about equal to that of ammonium 

 sulfate when not used in heavy applications. 



It should be incorporated with the soil at least a week 

 before planting, as it may injure the young plants if de- 

 composition has not proceeded far enough to remove its 

 somewhat toxic properties. As it must undergo this 

 decomposition before its nitrogen becomes available to 

 the young plants, there is an added reason for this pre- 

 caution. It does not give its best results as a top-dressing 

 because it requires incorporation with the soil for its 

 proper decomposition. 



427. Calcium nitrate. — The other process for com- 

 bining atmospheric nitrogen is of more recent invention 

 than that for the manufacture of calcium cyanamid but 

 is not conducted on a commercial scale in this country; 

 however, with the vast opportunities for developing elec- 

 tric power which are offered in certain localities, factories 

 for the manufacture of calcium nitrate will some day be 

 established. 



The process employs an electric arc to produce nitric 



