242 The Power of Soils to 



and we now embrace an early and seasonable opportunity to 

 supply it, assured that it will be read with satisfaction by 

 every cultivator : 



The power of absorbing and retaining ammonia, which 

 most experiments have shown the soil to possess, probably 

 will explain the reasons why in certain cases, on particular 

 soils, and applied to particular plants, the salts of ammonia 

 sometimes appear to produce little benefit. Several observers 

 have at different times stated, that to their great surprise, 

 they had found many of the salts of ammonia, not only with- 

 out any beneficial influence on vegetation, but even abso- 

 lutely hurtful to plants. 



It was this which some years since led Boussingault to 

 the conclusion, that salts of ammonia were only useful to 

 plants when the ammonia was either combined with carbonic 

 acid or some destructible organic acid. 



Plants fed with water alone, or planted in pure siliceous 

 sand, and watered with solutions of various salts of ammonia, 

 in place of being benefited, were killed ; although the same 

 plants, when grown in common soil, and watered with the 

 same ammoniacal solutions, were certainly rendered more 

 healthy and vigorous. The conclusion to which Boussingault 

 was at last led, was, that the only carbonate, and, therefore, 

 that in all cases where the other salts of this alkali were used 

 as manure, the acid must, by some process of chemical de- 

 composition, be removed, and replaced by the carbonic. A 

 key to some of the difficulties Avhich these observers could 

 not explain is now given to us, in the fact that an ordinary 

 fertile soil possesses the power of decomposing the salts of 

 ammonia, and by the acid of lime displacing the acid with 

 which the ammonia is combined. It has often been stated 

 by careful observers that they could find no difference in the 

 relative value of the various salts of ammonia as manure, and 

 that they all acted perfectly alike on plants ; this is not what 

 might reasonably be expected, but it would, of course, folloAV 

 as a necessary consequence from the power of the soil which 

 has lately been brought to light. 



