COMMERCIAL FERTILISERS 385 



and 1 per cent, of phosphoric acid; coal ashes 

 contain no plant food whatever but may benefit 

 the soil by improving the texture. 



German Potash Salts. Deposits of crude potash 

 salts in Germany were discovered in 1859. Min- 

 ing was begun in 1862 and the product of the 

 mines is now about 750,000 tons a year. The 

 supply seems inexhaustible. Three kinds of Ger- 

 man potash salts are commonly used in this country : 

 kainit, muriate of potash, and sulphate of potash. 



Kainit is one of the crude salts, just as it comes 

 from the mines. It contains about 12 per cent, of 

 actual potash and 33 per cent, of common salt, 

 together with other salts. This extremely large 

 percentage of salty material makes kainit un- 

 desirable for the heavier soils and for some crops; 

 but it is beneficial to light soils, and to certain 

 crops, as asparagus, that appreciate salt. Since 

 it contains so low a per cent, of potash, a pound of 

 potash in kainit costs more than a pound in the 

 refined salts. For this reason it is rarely used 

 except when its indirect benefit, because of its 

 saltiness, is needed. Sylvinit, another crude salt, 

 is very little used in this country. 



Muriate of Potash is used in the United States 

 more than any other potash fertiliser. It is very 

 highly concentrated, containing about 50 per cent, 

 of actual potash. Potash in muriate at $40 per 

 ton costs four cents a pound, which makes this the 

 cheapest source of potash. 



There are two occasions when muriate of potash 

 should not be used. Certain crops, notably to- 

 bacco, sugar beets, onions, and potatoes, are quite 

 noticeably injured by the chlorine which this salt 

 contains in large amounts. Again, if the soil is 

 deficient in lime, heavy applications of muriate 



