192 



Fertilisers 



[PT. Ill 



large firms controlling the industry to ensure continuity 

 of supplies for the future. The Ichaboe guano used in 

 South Africa is collected annually after the breeding 

 season is over: it is thus the freshest on the market. It 

 usually contains less phosphate and more sand than the 

 Peruvian guano of corresponding grade. 



The phosphatic guanos are obtainable from a wider 

 area and show larger proportions of phosphates and 

 rock material by reason of the removal of the organic 

 matter. 



The composition of these guanos is as follows: 



The high grade Peruvian guanos are used in horti- 

 culture, the ordinary grades in market gardens and 

 occasionally for potatoes. It is quick acting and its 

 effect at Rothamsted only lasts for one season (Table 

 XIV) ; it is somewhat superior to rape cake and shoddy, 

 but not to sulphate of ammonia^. The phosphatic 

 guanos are used both in market gardens and on farms. 

 Other grades are treated Avith sulphuric acid to 

 decompose the phosphates and form "dissolved guano," 

 which is used in intensive cultivation here and on sugar 

 plantations in the West Indies. 



1 Rothumsled Annnal Rpl., 1917; Leeds Bull. No. 3. 1898. 



