Section III.— THE POTASSIUM GROUP OF 

 FERTILIZERS 



For some years past the German potash manures have com- 

 pletely eclipsed other sources of potash, and it is only since 

 the war that non-German sources have once again come into 

 prominence. There is little doubt that the German potash 

 manures originated in the same way as most salt deposits, 

 that is to say, sea water has been naturally evaporated, 

 producing sodium chloride, then complex salts of magnesium 

 and potassium sulphates or chlorides, together with a deposit 

 of calcium sulphates. The material put upon the market 

 as kainit has, for a long time, had little connection with the 

 mineral properly so named, but has simply been a blend 

 graded to i2| per cent, pure potash (KgO), the remainder of 

 the material being chiefly sodium chloride, with some mag- 

 nesium sulphate. The composition of the German kainit 

 manure has been very constant, the average over many years 

 past having been 12*50 ±0*38 per cent. K2O for any single 

 sample. Other important potash manures of German origin 

 have been the sulphate and the muriate (chloride). The 

 better qualities of these have been about 90 per cent, purity, 

 but lower grades have also been on the market. They have 

 always been sold under guarantee. 



A very old type of potash manure is wood ash. The 

 ashes of full-grown timber do not contain much potash, but 

 the ashes of small twigs are fairly rich. The table on 

 p. 38 will roughly show the amount of potash in many 

 types of wood ashes. 



The ashes of coal contain hardly any potash, but certain 

 particular wind-blown coal ashes in industrial concerns 

 contain appreciable quantities of potash. The dust deposited 



