210 WALL'S MANUAL 



elements of the salts ; they enter into new com- 

 binations, the base and the acid being often separated 

 by the action of the living plant. 



We will illustrate this action : Suppose there be 

 applied to the soil a salt composed of muriatic acid 

 and soda (which is common table salt). By the 

 action of the living plant this salt is partially decom- 

 posed, that part of the soda furnishes direct food for 

 plants, and the rest with the muriatic acid acts as 

 solvents in the soil, and in that way nourishes vege- 

 tation. But the farmer should distinctly understand 

 that large crops, resulting from the use of salt, is at 

 the expense of his soil. Therefore salt should only 

 be used in small quantities, and always composted 

 with other manures. 



Again, let us take another illustration : Suppose 

 sulphate of lime (land plaster, or as it is generally 

 known, plaster of Paris), be applied to the soil, the 

 effect of only one bushel per acre is wonderful to 

 behold on clover or grass lands, which shows its good 

 effects as far as the eye can reach. It is almost 

 incredible that so small a quantity could act at all, 

 yet how beautifully is it explained by the principle 

 that plants dissolve this salt, the lime is separated 

 from the sulphuric acid, both of which are direct food 

 for plants ; yet its supplying these ingredients to the 

 soil is but rarely the main cause of its good effect 

 upon crops. It .has a great attractive power for 

 ammonia and carbonic acid contained in the air, both 

 of which it attracts and fixes in the soil. The lime, 

 carbonic acid and ammonia act as solvents of the 

 silicates in the soil, and the potash, soda, etc., of the 

 silicates is liberated to become food for plants. 



