On Agricultural Chemistry. 



25 



assumed according to the theory of Professor Liebig. It is seen, 

 too, that it is only in the later seasons that the available minerals 

 have appeared to be in defect, in relation to the nitrogenous 

 supply. 



That the mineral constituents are indeed becoming deficient in 

 several of the plots of our experimental fields, we have in our 

 collective results, as well on turnips and beans as on wheat, 

 abundant evidence ; and as the circumstances under which this 

 point has actually been arrived at, are well understood, we are the 

 better able to speak with confidence as to the non-exhaustion of 

 them in other cases. Of this we shall on some future occasion 

 speak much more in detail, when we are able to bring forward 

 more of the experimental facts relating to it than we can do in a 

 mere outline of this kind. But the plots to which we shall now 

 refer will afford some illustration of it. 



We have seen, then, that on Plot 10a there has been in every 

 year since the first experimental one a large amount of ammo- 

 niacal salts, but without mineral supply ; and that by this means 

 we have in every year obtained a considerable amount of produce 

 beyond that without manure. In Plots 18^, 185, and \7b, on 

 the other hand, we have in every year mineral supply ; and in 1846, 

 and ever since, this has been the same for these three plots, and 

 always very liberal in nearly all the constituents required by the 

 crop, — and in addition to this very liberal mineral provision, we 

 have in each year, on one or more of these plots, exactly the 

 same ammoniacal supply as in Plot 10 a, which had no mineral 

 manure, so that we are thus enabled to show at what point the 

 mineral supplies of the native soil were, in 10 deficient, in 

 relation to the quantity of ammonia artificially applied to it. For 

 the particulars of the manures of Plots 18<2, iSb, and \7h, we 

 must refer the reader to Tables 7, 8, 9, respectively, but the com- 

 parisons of produce to which we wish now to call attention will be 

 better seen in the summary table, No. 11. 



Thus, taking the cases of exactly similar ammoniacal supply, 

 but in Plot 10a without mineral, and in the plot compared with 

 it, loith minerals, we have in 1845, — 



On Plot 10a, 31f bushels of dressed corn and 4266 lbs. of straw, by 

 168 lbs. each, of sulphate and muriate of ammonia. 



On Plot 18, 33 bushels of dressed corn and 3819 lbs. of straw, with only 

 112 lbs. each, of the ammoniacal salts, but with mineral manure. 



In 1846, with equal ammoniacal supply in the two cases, we 

 have, — 



On Plot 10a, 27;^ bushels of dressed corn and 2244 lbs. of straw, without 

 minerals. 



On Plot Vjb, 30^ bushels of dressed corn and 2784 lbs. of straw, with 

 minerals. 



