THE SOIL 



before being used by plants. For this reason it should be 



applied in small quantities and at intervals of a few weeks. 



Potash is obtained in Germany, where it is found in 



several forms. It is put upon the market as muriate of 



FIG. 15. THE COTTON PLANT WITH AND WITHOUT FOOD 



In left top pot, no plant food ; in left bottom pot, plant food scanty ; in both 

 right pots, all elements of plant food present 



potash, sulphate of potash, kainit, which contains salt as 

 an impurity, and in other impure forms. Potash is found 

 also in unleached wood ashes. 



Phosphoric acid is found in various rocks of Tennessee, 

 Florida, and South Carolina, and also to a large extent in 



