O/i Agricultural Chemistry. 



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The importance of the subject, on sucli hig-h authority as that 

 of Professor Liebig himself, as thus stated, will, we trust, be con- 

 sidered sufficient reason for bringing before the readers of this 

 Journal a brief statement of the opinions to which our results 

 have led us ; but as Professor Liebig has said, in regard to our 

 experiments, that they are entirely devoid of value, as the foun- 

 dation for general conclusions;" and, further, that " with a know- 

 ledge of our experience of the effects of fallow and of production 

 on the large scale, it requires all the courage derived from the 

 want of intimate acquaintance with the subject" to make the 

 statements we have done, it seems incumbent on us to recall 

 attention to the plan and object of the experiments themselves, 

 before entering upon the consideration of the results which they 

 have provided. 



Looking upon the subject in a chemical point of view only, it 

 would seem that an analysis of the soil upon which crops were to 

 be experimentally grown, as well as a knowledge of the compo- 

 sition of the crop, should be the first points attained, with the 

 view of deciding in what constituents the soil was deficient ; and 

 at the commencement of our more systematic course of field ex- 

 periments the importance of these points was carefully considered. 

 When we reflect, however, that an acre of soil six inches deep 

 may be computed to weigh about 1,344,000 lbs. (though the roots 

 of plants take a much wilder range than this), and taking the one 

 constituent of ammonia or nitrogen as an illustration, that in add- 

 ing to this quantity of soil a quantity of ammoniacal salt con- 

 taining 100 lbs. of ammonia — which would be an unusually 

 heavy and very effective dressing — we should only increase the 

 per-centage of ammonia in the soil by 0*0007, it is evident that 

 our methods of analysis would be quite incompetent to appreciate 

 the difference between the soil before and after the application, — 

 that is to say, in its state of exhaustion, and of highly productive 

 condition, so far as that constituent is concerned ; and from our 

 knowledge of the effects of this substance on wheat, we may con- 

 fidently assert that the quantity of it supposed above w^ould have 

 given a produce at least double that of the unmanured land. The 

 same kind of argument might, indeed, be adopted in reference to 

 the more important of those constituents of a soil which are found 

 in the ashes of the plants grown upon it, and we determined, 

 therefore, to seek our results in another manner. Indeed, the 

 imperfection of our knowledge of the productive quality of a 

 soil, as derived from its percentage composition, has been amply 

 proved by the results of analysis which have been published dur- 

 ing the last ten years ; and in corroboration we need only refer to 

 the opinions of Professor Magnus on this subject, who, in his 

 capacity of chemist to the Landes-Oekonomie Kollegium " of 



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