CAUSE OF INACTIVITY OF NITROGEN IN SOILS. 319 



but have been observed in altogether different districts, 

 and which must at least remain doubtful as far as their 

 appHcation to his own land is concerned. 



If, during the last ten years, only one farmer in a 

 thousand had resolved to institute experiments upon his 

 own land with ammonia or salts of ammonia to test the 

 theory, whether in fiict this manure is useful beyond all 

 others in increasing the corn crops, how soon and how 

 easily would an accurate estimate have been formed of its 

 true value by other farmers ! 



The simple reflection that not one of the substances 

 nutritive to plants does of itself exert any influence upon 

 theii' growth, and that several other substances must be 

 present, if the first is to prove useful, should have brought 

 him to the conclusion that the case cannot be otherwise 

 with nitrogen ; and that the value of a manure cannot be 

 measured ^y the amount of nitrogen which it contains ; 

 for this presupposes that the nitrogen possesses an opera- 

 tive power, which must manifest itself under all circum- 

 stances, and that the money which the farmer lays out in 

 its purchase -will always ensure an adequate return. 



Now, when his common sense tells him that such a 

 supposition is impossible, and that he has only to open his 

 eyes to observe by innumerable facts that ammonia is no 

 exception to other nutritive substances, he will of himself 

 come to the conclusion that the inactivity of the gi'eat 

 mass of nitrogen in his field is not due to any condition 

 pecuUar to itself, which science can neither investigate nor 

 explain, but that it is inactive, just as phosphoric acid, 

 potash, lime, magnesia, silicic acid, and iron, are inactive, 

 ^vhen there is wanting in the ground one of the conditions 

 necessary to make them available. 



The theoiy that by far the greater portion of tlie niti-o- 

 gen in the ground is incapable of serving for the nutrition 



