CHAPTEK XY. 

 NITROGEXIZED PHOSPHATIC MANURES. 



Concentrated manures containing both nitrogen and phosphoric 

 acid in important quantities are only represented on the market 

 under well-determined forms. Such manures have played a very 

 important role in the history of agriculture. They were the starting- 

 point of chemical manures, and it is through them that we first 

 learned to fertilize the soil and to increase the vegetable production^ 

 otherwise than by farmyard manure. It was only afterwards that 

 agriculture came to the large series of phosphates, potash salts and 

 nitrogenous matter which have to-day become the indispensable 

 factors of all rural exploitation. These manures are Peruvian guanO' 

 and bones, to which had to be added gradually the different manures 

 composed from waste of animal origin described in the preceding 

 chapters. 



Peruvian Guano. — Its Comjjosition. — Like phospho-guanos 

 already described, Peruvian guano is essentially a product of the 

 decomposition of the excrements of sea-fowl. It has an analogous 

 origin, but is formed in a different manner ; whilst Baker guano 

 scarcely contains 1 per cent of nitrogen with about 80 per cent of 

 phosphate of lime, Peruvian guano has preserved almost integrally 

 throughout centuries the nitrogenized organic matter, owing to the 

 climatic conditions which supervene in the countries where such 

 deposits are found. Birds' excrement (pigeons' and hens' dung) has- 

 been known for a long time as a valuable manure ; . it is dis- 

 tinguished by great richness in nitrogen, contrary to what occurs in 

 the case of mammals. But the excrements of birds of prey 

 (carnivorse) are particularly rich in nitrogen, and the sea-birds- 

 which produce guano fall exactly into this category ; whilst in fact 

 the dried mixture of the solid and liquid dejections of man contain 

 on an average 10-4:0 per cent of nitrogen and 3-88 per cent of 

 phosphoric acid, the dried dung of the eagle contains 35-7 to 37-7 

 of nitrogen and 0*32 to 3'99 of phosphoric acid. This explains why 

 the guano of sea-birds is very rich in nitrogen, whilst the urine of 

 these birds, instead of being liquid like that of mammals, is thick, 

 and thus does not penetrate into the soil. 



The deposits of nitrogenized guano extend over a vast surface of 

 the West Coast of South America, its quality always varying 



(278) 



