166 MANURES. VII. 



Of the 70,877 tons of chloride used in Germany only about 

 1528 tons were employed in agriculture, the rest being used as 

 the raw material for the production of other potash salts. Of 

 the 107,107 tons exported, however, about 64,000 tons were 

 employed for agricultural purposes, the extra cost of this 

 material over the raw products, kainite, &c., being compensated 

 by the greater cheapness of its transport, owing to its high 

 potassium content. The same is true of potassium sulphate, 

 which in Germany is chiefly used in the preparation of alum, 

 not more than a third of the quantity given in the table being 

 used as a fertiliser, while of that exported more than seven- 

 eighths of the total is employed in agriculture.'" 



In this country the products employed are mainly kainite, 

 the calcined double sulphate of potash and magnesia, and the 

 "muriate of potash." For special horticultural purposes pure 

 sulphate of potash and nitrate of potash are also employed. 



The important potash manures contain their potassium either 

 as chloride or sulphate. The chloride has the advantage in 

 being more diffusible in the soil ; but in most other respects 

 the sulphate is preferable. As in the case of other soluble 

 manures, interaction between the potassium salt and the cal- 

 cium and other compounds in the soil begins immediately, re- 

 sulting in the formation of calcium chloride or sulphate. The 

 former has an injurious action upon plants, while the latter is 

 harmless or probably beneficial. Moreover, when potassium 

 chloride is applied in large quantities, the salt as a whole seems 

 to be absorbed by some plants, and in the case of tobacco, for 

 example, the ash left when the dried plant is burnt contains the 

 easily fusible potassium chloride. This acts as a fire-proofing 

 material to some extent and prevents the proper burning of the 

 tobacco ; potassium sulphate yields a crop containg no such 

 fusible ash constituent. In the case of clover, corn, and grass, 

 however, potassium chloride appears to have little or no harm- 

 ful effect. 



Potash manures are most needed on light sandy or calcareous 

 soils and are seldom required on clay land. Potatoes, grass 

 land, and leguminous crops are particularly benefited by potash 

 manures. They are best applied in the autumn or winter so as 



* Sammel-Austellung der Deutschen Chemist-hen Industrie, Paris Exhibition, 1900. 



