222 THE WEALTH OF THE SEA 



muck soils which already contain an excess of organic 

 matter and consequently much nitrogen. Phosphorus- 

 containing fertilizers stimulate the formation of 

 fruits and grains. Thus fish scrap is an excellent 

 fertilizer for corn, which requires much nitrogen for 

 growth and also phosphorus for grain formation. 



Relatively little fish scrap is sold direct to the 

 farmers, however ; most of it is bought by manufac- 

 turers of mixed fertilizers, who grind it and mix it 

 with potassium salts and other fertilizer ingredients 

 in order to make a complete balanced fertilizer. Some 

 fish scrap is not dried but after being thoroughly 

 pressed is acidified with sulphuric acid. This product, 

 which is termed green or acidulated scrap, is sold 

 direct to the farmers. Such scrap cannot be mixed 

 with other fertilizer ingredients, as it contains too 

 much moisture, but the acid acts as a preservative 

 and keeps it from rotting. This grade of fish scrap 

 is seldom shipped any great distance but is sold to 

 the farmers residing near the menhaden factories. 



Most of the fish scrap produced along the Pacific 

 coast of the United States is prepared especially 

 for use as feed. Some menhaden scrap is now used 

 as meal, and each year more is used in this way. The 

 ordinary menhaden scrap is suitable for the feeding 

 of animals, but it can be made much more palatable 

 by improved methods. Menhaden scrap is ordinarily 

 dried in rotary hot-air driers, in which the products 

 of combustion of coal or oil enter the same end of the 

 revolving driver. The gases are very hot and often 

 scorch the scrap, making it unfit for use as meal. 

 Steam-heated driers must be used if a high-grade 



