120 GUANO 



covering the manure with earth was shown to greatly preserve the 

 nitrogen, while allowing of the fermentation and consequent loss of the 

 carbonaceous matter ; superphosphate and kainite, which also prevent 

 loss of nitrogen, when applied at the rate of about 2 per cent of the 

 manure, interfere with other fermentative changes and allow the straw 

 to remain practically intact. Hence they act as antiseptics rather than 

 absorbents. 



Other Organic Manures. A number of other refuse matters of 

 vegetable or, more frequently, animal origin are used as manures, the 

 chief being 



Guano. 



Pigeon and fowl dung. 



Fish refuse or fish guano. 



Sea-weed. 



Dried blood. 



Meat meal or meat guano. 



Bones. 



Woollen refuse, shoddy manure. 



Soot. 



Oil -cakes and oil- seed refuse. 

 These can only be briefly dealt with here. 



Guano is the dried dung of sea-birds, together with portions of 

 their feathers, bones, and the refuse of their food ; the older deposits 

 also contain the remains of seals, walruses, etc. Guano accumulates 

 on islands or near the coasts in tropical climates, the chief deposits 

 being found in North and South America, Africa, Australia, the West 

 Indies, and islands in the Pacific. The original Peruvian guano, the 

 deposits of which are now exhausted, was a very valuable and con- 

 centrated manure, containing nearly half its weight of ammonium 

 salts urate, C 5 H 3 (NH 4 )N 4 3 , oxalate, (NH 4 ) 2 C 2 O 4 , and phosphate, 

 (NHJgPO 4 , together with calcium phosphate and potash compounds. 



It contained from 11 to 16 per cent of nitrogen and from 10 to 12 

 per cent of phosphorus pentoxide. 



The guano now obtainable contains much less nitrogen (about half 

 or a little more), though often much more phosphates. 

 Two varieties of guano are now imported : 



(1) Nitrogenous and phosphatic. These have accumulated in 

 practically rainless districts and the excreta which formed them have 

 been desiccated before much fermentation was possible. True Peruvian 

 guano from the Chincha Islands, and Ichaboe guano, a recent deposit, 

 are examples of such guanos, the latter usually containing from 7 to 

 11 per cent nitrogen and 5 per cent phosphorus pentoxide. 



(2) Phosphatic. These are the remains left after the weathering 

 by rain, etc., of the dung of sea-birds. Owing to the moist state in 

 which it has been kept, the nitrogenous matter has been lost, by solu- 

 tion or volatilisation, and only the mineral (phosphatic) portion left. 



Considerable deposits of guano were discovered some years ago 

 on islands lying off Damaraland, on the West Coast of Africa, and are 

 being extensively worked. 



