Supplying Soil Needs 



m 



Robert Cusfiman Murphy 



FIG. 136. Part of a guano field on an island off the coast of Peru. The birds 

 are pelicans and cormorants, the principal producers of guano. 



other fertilizer. Ammonia is mostly made from coal How 

 as a by-product when illuminating gas is manufactured. c l ame i ^ e 

 Coal can be made to yield this nitrogen compound be- 

 cause coal was formed from vegetable matter. The 

 coal-forming plants took the nitrogen from the soil 

 millions of years ago (Fig. 135). 



Guano is a valuable commercial fertilizer that con- Guano 

 sists of the dung of sea fowls or bats. A good quality 

 of guano contains nitrogen, phosphorus, and potassium, 

 in compounds. Most of the old deposits of guano have 

 been exhausted. The supply that continues comes for 

 the most part from a number of islands off the coast 

 of Peru, where the guano-producing birds are carefully 

 protected by the government (Fig. 136). 



