246 



On Agricultural Chemistry. 



agricultural chemistry arises from the errors which have been 

 committed by its professors. They have endeavoured to account 

 for, and sometimes to pronounce as erroneous, the knowledge 

 which ages of experience have established ; and they have at- 

 tempted to generalise without the practical data necessary to 

 accomplish their end with success. Agriculture will eventually 

 derive the most important assistance from chemistry, but before 

 it can propose any changes in the established routine of the 

 farmer, it must, by a series of laborious and costly experiments, 

 explain this routine in a satisfactory manner. 



Although the experimental results which have been detailed 

 undoubtedly prove that to produce agricultural crops of corn 

 nitrogen must be supplied to the soil in some form or other, 

 two important questions still remain unanswered, namely, first, 

 what amount of ammonia will be required to produce a given 

 amount of corn? or, in other words, what amount of nitrogen 

 must the farmer accumulate in his soil to obtain each bushel of 

 corn beyond the natural produce ? Secondly, what are the most 

 economical means at his disposal for securing the necessary 

 supply? The solution of these questions is within the reach of 

 careful experiment and calculation ; and, although any data at 

 present at our disposal may be incompetent to a proper treatment 

 of them, it may serve some useful purpose to apply such results 

 as we possess with the view of directing some general and ap- 

 proximative knowledge on points bearing so essentially on the 

 economy of agriculture. 



[t may be considered for our present purpose that a bushel of 

 wheat contains one pound of nitrogen. It must not be supposed, 

 however, that \ \ lb. of ammonia (equivalent to one pound of 

 nitrogen) supplied to the soil, will, even under the most favour- 

 able circumstances, add a bushel to its natural produce. Through- 

 out the whole course of my experiments upon the growth of 

 wheat by means of ammoniacal salts there has been a loss of 

 nitrogen far too great to be attributed merely to drainage and 

 evaporation from the land ; and it is possible that a better know- 

 ledge than we now possess of the vital actions of plants will, 

 sooner or later, throw much light upon this interesting and highly 

 important phenomenon. I am inclined to think that, for prac- 

 tical purposes, we may assume 5 lbs. of ammonia to be required 

 for the production of every bushel of wheat beyond the natural 

 yield of the soil and season ; at any rate, it will be useful to re- 

 member this as the amount until future experiments shall furnish 

 further information on the subject. In the following table, p. 248, 

 are arranged some of the results obtained last year (harvest, 1846) 

 in my experimental wheat-field. 



Besides the bearing which these results have upon other points 



