106 THE ESSENTIALS OF AGRICULTURE 



crude salts from the mine are dissolved and recrystallized, thus 

 securing purer forms of potash salts for the fertilizer trade. 



126. Potassium chloride. Potassium chloride, otherwise known 

 as muriate of potash, is the most common of the purified potash 

 salts, and contains about 42 per cent of potassium. It has a some- 

 what injurious effect upon the quality of potatoes and tobacco, 

 but for other farm crops, it is a very satisfactory form to use. 



FIG. 44. Wheat under different kinds of soil treatment 



The field at the right had no soil treatment ; on that at the left a crop of legumes was 

 plowed under, and phosphorus and lime were used 



127. Potassium sulphate. Potassium sulphate is another form 

 of potash salt secured by purifying the raw salt from the potash 

 mines. It contains about 43 per cent of potassium in its com- 

 mercial form. It is extensively used as a fertilizer and as an 

 ingredient of mixed fertilizers. It has no injurious effect upon 

 the quality of any of the farm crops and is the principal potas- 

 sium fertilizer used on potatoes and tobacco. 



128. Wood ashes. Wood ashes, on account of their abun- 

 dance and cheapness, were formerly much used in the Eastern 

 states. Fresh hardwood ashes contain about 30 per cent of lime. 

 The potassium is in the form of carbonate, which is alkaline, 

 and this with the lime tends to keep the soil sweet. Used in large 

 quantities, however, ashes are injurious to germinating seeds. 



