98 AGRICULTURE 



nous fertilizers. The most important commercial ferti- 

 lizers that are rich in nitrogen are cotton-seed meal and 

 nitrate of soda. If nitrogen occurs in mixtures with other 

 precious plant-foods, the fertilizer may be called an am- 

 moniated fertilizer, or "guano." Ammonia is a combination 

 of fourteen parts by weight of nitrogen with three parts 

 of hydrogen (Fig. 63). Fourteen pounds of nitrogen, 

 the most precious of plant-foods, may become seventeen 

 pounds of ammonia. Hence, if there is printed on a bag 

 . of fertilizer the state- 



ment that it contains 

 two per cent of nitro- 

 gen, you can calculate 

 how much ammonia 

 FIG. 63. SHOWING THE WEIGHT OF AMMONIA this equals, milltiply- 



EQUIVALENT TO 14 POUNDS OF NITROGEN 



ing the amount of 



nitrogen by 17 and dividing the product by 14. On the 

 other hand, if the printing on the bag shows that cotton- 

 seed meal contains eight and one-half per cent of ammonia, 

 change this to nitrogen by dividing by 17 and multiplying 

 by 14. The amount of ammonia is always larger, because 

 it contains all the nitrogen and another element besides. 



Cotton-seed meal. Cotton-seed meal is a yellowish, 

 powdery material made from the kernels of cotton seed 

 after removing most of the oil and hulls. Cotton-seed meal 

 is more than twice as rich in nitrogen as the whole cotton 

 seed from which it is made. 



Cotton-seed meal usually contains between six and seven 

 pounds of nitrogen in each hundred pounds of meal and 

 is therefore expensive. It also contains some phosphate 



