MISCELLANEOUS FERTILIZERS 193 



point : a buckwheat plot fertilized with salt produced 

 a crop with more potash and less sodium than a sim- 

 ilar unfertilized plot. 



Salt may be used to check the rank growth of straw 

 during a rainy season, and thus prevent loss of the 

 crop by lodging. It should not be used in excessive 

 amounts, as it is destructive to vegetation; 200 pounds 

 per acre is a fair application. Salt also improves the 

 physical condition of the soil by increasing the surface- 

 tension of the soil water. It should not be used on a 

 tobacco or potato crop, because it injures the quality 

 of the product. Salt is beneficial in preventing some 

 forms of fungus diseases from becoming established 

 in soils. 



259. Magnesium Salts. Magnesium is present in 

 the ash of all plants, and is an essential element of 

 plant growth. Usually soils are so well stocked with 

 this element that it is not necessary to apply it in fer- 

 tilizers. Some of the magnesium salts, as the chloride, 

 are injurious to vegetation, but when associated with 

 lime as carbonate, magnesia imparts fertility. In 

 many of the Stassfurt salts magnesium is present. 



260. Salt. The deposits formed in boiler flues and 

 chimneys when wood and soft coal are burned contain 

 small amounts of potash and phosphoric acid. Soot 

 is valuable mainly as a mechanical fertilizer and is 

 slow in decomposing. There is but little plant food 

 in soot, as shown by the following analysis: 



Soft coal soot. Hard wood soot. 



Percent. 14 Per cent. 70 



Potash 0.84 1.78 



Phosphoric acid 0.75 0.96 



('3) 



