Nitrogenous Fertilizers 45 



dung, and it is probably one of the oldest materials used 

 as a fertilizer. Its use dates back to the twelfth century, 

 but it was not until the middle of the nineteenth century 

 that its value became generally appreciated. The first 

 shipments were made from Peru to European ports late 

 in the year of 1840. The use of these products spread 

 rapidly and were considered a valuable source of nitrogen, 

 though at the present time they are not commercially 

 important, owing to the practical exhaustion of the best 

 supplies. Of the guanos, the product obtained from 

 Peru, or from the islands on the coast of that country, 

 is the richest in nitrogen. It is derived from the excre- 

 ments and bodies of sea-fowls. 



When the deposits occur in regions which are warm and 

 with little rainfall, they are high in nitrogen, especially if 

 considerable time has elapsed since their formation. 

 Where rainfall is more plentiful, even occasional, the 

 nitrogen is readily changed by microorganisms to soluble 

 forms which are leached away together with the potash 

 salts, leaving a product low in nitrogen and high in phos- 

 phoric acid. The first product usually contains from 12 

 to 14 per cent of nitrogen and from 10 to 12 per cent of 

 phosphoric acid, whereas the second product contains 

 from 5 to 8 per cent of nitrogen and from 20 to 25 per cent 

 of phosphoric acid. It must be remembered that guanos 

 are variable and each successive consignment shows a 

 different composition. In fact, the composition of these 

 materials is of a very complex character. The nitrogen 

 exists largely as ammonia, combined with oxalates, 

 urates, humates, sulfates, phosphates, carbonates, and to 

 some extent in purely organic form. In these forms the 

 nitrogen is quickly available, and marvelous results are 

 obtained from their use. 



