260 HANDY-BOOK OF HUSBANDRY. 



'•" Now there are certain salts, such as chloride of sodium, (com- 

 " mon salt,) nitrate of soda, and salts of ammonia, which experi- 

 '' ence has proved to exercise, under certain conditions, a favorable 

 " action upon the productiveness of a field. 



*' These salts, even in their most dilute solutions, possess, like 

 '' carbonic acid, the remarkable power of dissolving phosphate of 

 " lime and phosphate of magnesia ; and when such solutions are 

 " filtered through arable soil, they behave just like the solution of 

 " these phosphates in carbonic acid water. The earth extracts 

 '' from these salt solutions the dissolved earthy phosphates, and 

 " combines with the latter. 



" Upon arable soil mixed with earthy phosphates in excess, 

 " these salt solutions act in the same way as upon earthy phos- 

 " phates in the unmixed state, that is, they dissolve a certain pro- 

 ^' portion of the phosphates. 



" Nitrate of soda, and chloride of sodium suffer, by the action 

 " of arable soil, a similar decomposition to that of the salts of 

 *■'■ potash. Soda is absorbed by the soil, and in its stead lime or 

 *■'■ magnesia enters into solution in combination with the acid. 



" If we compare the action of arable soil upon salts of potash 

 " and salts of soda, we find that the soil has far less attraction for 

 " soda than for potash ; so that the same volume of earth which 

 " will suffice to remove all the potash from a solution will, in a 

 " solution of chloride of sodium or nitrate of soda of the same 

 '' alkaline strength, leave undecomposed three-fourths of the dis- 

 *' solved chloride of sodium, and half of t^ie nitrate of soda. 



" If, therefore, a field exhausted by culture, which contains 

 " earthy phosphate scattered here and there, is manured with 

 *' nitrate of soda or chloride of sodium, and by the action of rain 

 *■'■ a dilute solution of these salts Is formed, a portion of them will 

 "remain undecomposed in the ground, and must in the moist 

 " soil exert an influence, weak in itself, but sure to tell in the 

 " long run. 



" Like carbonic acid generated by the putrefaction of vegetable 

 '■'■ and animal substances, and dissolving in water, these salt 

 " solutions become charged with earthy phosphates in all places 



