CHAPTER XI 

 POTASH FERTILIZERS 



The third of the fertilizer trio is potassium or, as it is 

 usually called, potash. The element potassium occurs in 

 most soils to a very considerable extent (Section 144 b, 6), 

 but it is frequently present in an unavailable form. Some 

 plants, notably clover and alfalfa, require considerable 

 potassium; and other crops also remove it to no small 

 extent. Unlike nitrogen and phosphorus, however, potas- 

 sium is not sold from the farm in any considerable amount 

 except in hay, since it occurs for the most part in the stems 

 and leaves of plants. These are the portions of the crop 

 which usually remain on the farm, being fed as roughage or 

 used as litter. In this way the potassium gets back to the 

 soil. Its application, however, frequently results in increased 

 yields, and it is thus an important element in fertilizers. 



177. The German Potash Deposits. — The most important 

 source of potassium in the world is located at Stassfurt in 

 northern Germany where there are today over one hundred 

 mines producing potash salts (Fig. 53) . For several centuries 

 common salt had been obtained from its salt springs and 

 wells. About the middle of the nineteenth century deep 

 borings revealed the presence of immense beds of rock salt 

 at a depth of about 1000 feet. Overlying these beds of salt, 

 however, were considerable deposits of potassium and 

 magnesium compounds. These salts were considered worth- 

 less at the time and were thrown away, but later their value 

 became apparent, until now the potash salts are the only 

 ones of value. Rock salt is no longer mined at Stassfurt. 



It is believed that in past geologic ages there existed 

 here an immense inland sea which was probably fed inter- 

 mittently by inrushes of water from the ocean outside. 



