98 FIRST PRINCIPLES OF AGRICULTURE. 



the planting of the crop, in order to avoid danger to 

 the young plant from an excess of magnesia salts, 

 which injure the tender rootlets of plants, and also that 

 the excess of chlorides, which sometimes influence un- 

 favorably the quality of the produce, may be washed 

 from the surface soil by the rains. 



In Germany, where the use of these potash compounds 

 has received most careful study, their application is 

 almost invariably made in the fall of the year, or upon 

 the crop preceding the one which is in especial need 

 of potash fertilization. In this country, owing to our 

 heavy spring rains, an early spring application will 

 doubtless answer quite as well in most cases. 



Muriate of Potash. This salt is manufactured from 

 the crude forms, and is the richest in potash of the 

 Stassfurt products. It varies in composition according 

 to the method of manufacture, the commercial products 

 being divided into three grades. The grade most com- 

 monly met with upon the markets here contains about 

 fifty per cent actual potash, or potassium oxide. The 

 chief impurity is common salt, or sodium chloride ; the 

 lower the content of potash, the higher the content of 

 sodium salts. This form of potash is perhaps more 

 largely used than any other. 



Sulphate of Potash. This form of potash, often 

 called "high-grade sulphate," is regarded as preferable 

 to the "muriate" for many crops, particularly sugar- 

 beets, tobacco, potatoes, and fruit, chiefly because of its 

 more favorable influence on the quality of the produce. 

 It is, however, more expensive than the muriate, and is 

 not so largely \ised by the manure-makers. Its effect 



