522 SOILS: PROPERTIES AND MANAGEMENT 



salts from which plants absorb acid in larger amounts 

 than they do bases decrease availability, or at least do not 

 affect it, while salts from which plants absorb the bases in 

 $ij|£er quantity than the acids have a tendency to render 

 the pfrosfhaje more available, because of the solvent 

 action of theffc^d. 



FERTILIZERS USED FOR THEIR POTASSIUM 



The production of potassium fertilizers is largely con- 

 fined to Germany, where there are extensive beds varying 

 from 50 to 150 feet in thickness, lying under a region of 

 country extending from the Harz Mountains to the Elbe 

 River ancL known as the Stassfurt deposits. Deposits 

 have lately been discovered in other parts of Germany. 



441. Stassfurt salts. — The Stassfurt salts contain 

 their potassium either as a chloride or as a sulfate. The 

 chloride has the advantage of being more diffusible in the 

 soil, but in most respects the sulfate is preferable. Potas- 

 sium chloride in large applications has an injurious effect 

 on certain crops, among which are tobacco, sugar beets, 

 and potatoes. On cereals, legumes, and grasses, the 

 muriate appears to have no injurious effect. 



The mineral produced in largest quantities by the 

 Stassfurt mines is kainit. Chemically it consists of mag- 

 nesium and potassium sulfate and magnesium chloride, 

 or of magnesium sulfate and potassium chloride. Kainit 

 has the same effect on plants as has potassium chloride. 

 It contains from 12 to 20 per cent of potash and from 25 

 to 45 per cent of sodium chloride, with some chloride and 

 sulfate of magnesium. 



Kainit should be applied to the soil a considerable 

 time before the crop for which it is intended is planted. 



