POTASH-BEARING FERTILIZERS 341 



has the same action on plants as has potassium chloride. 

 It contains from 12 to 20 per cent of potash, and 25 to 

 45 per cent of sodium chloride, with some chloride and 

 sulfate of magnesium. 



Kainit should be applied to the soil a considerable 

 time before the crop for which it is intended is planted. 

 It should not be drilled in with the seed, as the action 

 of the chlorides in direct contact with the seed may 

 injure its viability. In addition to the potassium added 

 to the soil by kainit, there are also in this fertilizer 

 magnesium and sodium. The magnesium may be objec- 

 tionable if there is much already present in the soil. 

 (See page 350.) Sodium may to some extent replace 

 potassium in the soil economy, and in that way may be 

 beneficial. 



Silvinit contains its potassium both as chloride and 

 as sulfate. It also contains sodium and magnesium 

 chlorides. Potash constitutes about 16 per cent of the 

 material. Owing to the presence of chlorides, it has the 

 same effect on plants as has kainit. 



The commerical form of potassium chloride generally 

 contains about 80 per cent potassium chloride, or 50 

 per cent potash. The impurities are largely sodium 

 chloride and insoluble mineral matter. The possible 

 injury to certain crops from the use of the chloride has 

 already been mentioned. For crops not so affected, 

 potassium chloride is a quick-acting and effective carrier 

 of potassium, and one of the cheapest forms. 



High-grade sulfate of potassium contains from 49 

 to 51 per cent of potash. Unlike the muriate, it is not 

 injurious to crops but is more expensive. 



