On Agricultural Chemistry. 



7 



accumulate within the soil itself a sufficiently liberal supply of 

 those constituents found in the ashes of the plant — essentially 

 soil constituents, v»-e shall by this means be able in all cases to 

 increase thereby the assimilation of the veg-etable or atmospheric 

 constituents in a degree sufficient for agricultural purposes. But 

 agriculture is itself an artificial process ; and it will be found that, 

 as regards the production of wheat more especially, it is only 

 by the accumulation within the soil itself of nitrogen, naturally 

 derived from the atmosphere, rather than of the peculiarly soil- 

 constituents, that our crops of it can be increased. Mineral sub- 

 stances will indeed materially develop the accumulation of 

 vegetable or atmospheric constituents when applied to some of the 

 crops of rotation ; and it is thus chiefly that these crops become 

 subservient to the growth of the cereal grains ; but even in these 

 cases it is not the constituents, as found collectively in the ashes of 

 the plants to he grown, that are the most efficient in this respect ; 

 nor can the demand which we find thus made for the production 

 of crops in agricultural quantity be accounted for by the mere 

 idea of supplying the actual constituents of the crop. It would 

 seem, therefore, that we can only arrive at correct ideas in agri- 

 culture by a close examination of the actual circumstances of 

 growth of each particular crop when grown under cultivation. 

 We now turn to the consideration of our experiments upon this 

 subject. 



It has been said that all the experimental fields were selected 

 when they were in a state of agricultural exhaustion. The wheat- 

 field, however, after having been manured in the usual way for 

 turnips at the commencement of the previous rotation, had then 

 grown barley, peas, wheat, and oats, without any further manur- 

 ing; so that when taken for experiment in 1844, it was, as a grain- 

 producer, considerably more exhausted than would ordinarily be 

 the case. It was, therefore, in a most favourable condition for the 

 purposes of our experiment. 



In the first experimental season, the field of 14 acres was divided 

 into about 20 plots^ and it was by the mineral theory that we were 

 mainly guided in the selection of manures ; mineral manures were 

 therefore employed in the majority of cases. Ammonia, on the 

 other hand, being then considered as of less importance, was used 

 in a few instances only, and in these in very insignificant quantities. 

 Rape-cake, as being a v»'ell-recognised manure, and calculated to 

 supply — besides some minerals and nitrogen — a certain quantity 

 of carbonaceous substance in which both corn and straw so much 

 abound, was also added to one or two of the plots. 



The results of this first season (1844) having already been 

 pretty fully detailed in this Journal, we can only give a summary 

 of them in this place : — 



