OTHER FORMS OF ORGANIC NITROGEN 333 



and wool-and-hair waste, which last two, on account 

 of their mechanical condition, are of practically no value. 



The meals made from seeds are primarily stock-foods, 

 but are sometimes used as manures. They decompose 

 rather slowly in the soil, owing to their high oil content, 

 and are much more profitably fed to live stock than 

 applied as farm manure. They contain some phosphorus 

 as well as nitrogen. 



Guano consists of the excrement and carcasses of 

 sea-fowl. The composition of guano depends upon the 

 climate of the region in which it is found. Guano from 

 an arid region contains nitrogen, phosphorus and potas- 

 sium, while that from a region where rains occur con- 

 tains only phosphorus the nitrogen a-nd potassium 

 having been leached out. In a dry guano the nitrogen 

 occurs as uric acid, urates, and, in small quantities, 

 as ammonium salts. A damp guano contains more 

 ammonia. The phosphorus is present as calcium phos- 

 phate, ammonium phosphate, and as the phosphates of 

 other alkalies. A portion of the phosphate is readily 

 soluble in water. All of the plant-food is thus either 

 directly soluble, or becomes so soon after admixture 

 with the soil. The composition is extremely variable. 

 The best Peruvian guano contains from 10 to 12 per cent 

 of nitrogen, 12 to 15 per cent phosphoric acid, and 3 to 4 

 per cent of potash. 



Guano was formerly a very important fertilizing 

 material, but the supply has become so nearly exhausted 

 that it is relatively unimportant at the present time. 



Of the abattoir products, dried blood is the most 

 readily decomposed, and therefore has its nitrogen 



