The following favorable results are reported from a heavy soil in 

 Germany : 



TABLE NO. 16 



YIELD OF OATS AND STRAW PEE ACRE WITH 

 DIFFERENT MANURING 



The following table, given by the Massachusetts Experiment Station, 

 is very interesting: 



TABLE NO. 16 .. COW PEAS AND SOY BEANS FOR GREEN MANURING 



COMMERCIAL FERTILIZERS 



COMMERCIAL fertilizers are carriers of plant food in an available 

 and concentrated form. They contain the three principal elements 

 needed in crop production, namely, nitrogen, phosphorus and potash. 

 Nitrogen is usually referred to as ammonia; phosphorus as available 

 phosphoric acid, and potash as potassium. The ammonia is derived 

 from various animal and vegetable sources such as dried blood, tankage, 

 bones, hoof and horn meal, cottonseed meal, ground fish, and guano; 

 also from sulphate of ammonia, nitrate of soda, and nitrate of potash. 

 Commercial nitrogen is also extracted from the air. The sources of 

 phosphoric acid are : phosphate rock, phosphate slag, raw bone, bone ash, 

 steamed bone, bone black, and guano. These substances are treated 

 chemically, rendering them soluble. Potash is secured from kainite, 

 muriate of potash, sulphate or potash, and other potash salts and wood 

 ashes. Prior to the war, potash came from Germany in the form of sul- 

 phate, muriate, and kainite. 



The percentage of amounts of available plant food elements in a com- 

 plete fertilizer is usually marked on the package. In most states, the 

 inspection is quite rigid. To the credit of the standard commercial fer- 

 tilizer firms, it has been found, upon analysis, that the amount specified 



