Ivi REPORT — 1856. 



But I may be permitted to remark, that whilst some points of difference 

 between them still remain open for further investigation, a much nearer 

 correspondence of opinion exists with respect to others, than the public in 

 general, or even perhaps the disputants themselves, are inclined to allow. 



In so far, indeed, as concerns the relative advantages of mineral and 

 ammoniacal manures, I presume there is little room for controversy ; for 

 although most soils may contain a sufficiency of the inorganic constituents 

 required by the crop, it by no means follows that the latter are always in an 

 available condition; and hence it may well happen that in most cases in 

 which land has been long under cultivation, the former class of manures 

 becomes, as Baron Liebig asserts, a matter of paramount necessity. Now 

 that the same necessity exists for the addition of ammoniacal manures can 

 liardly be contended, when we reflect, that at the first commencement of 

 vegetable life, every existing species of plant must have obtained its nourish- 

 ment, solely from the gaseous constituents of the atmosphere, and from the 

 mineral contents of the rock in which it vegetated. 



The only divergence of opinion therefore that can arise, relates to the 

 degree of their respective utility in the existing state of our agriculture, and 

 to the soundness of Baron I,iebig's position, that a plant rooted in a soil well- 

 charged with all the requisite mineral ingredients, and in all other respects 

 in a condition calculated to allow of healthy vegetation, may sooner or later 

 be able to draw from the atmosphere whatever else is required for its full 

 development. 



And does not, I would ask, this latter position derive some support from 

 the luxuriant vegetation of the tropics, where art certainly contributes nothing 

 towards the result? and is it not also favoured by such experiments as those 

 carried on at Lois Weedon in Northamptonshire, where the most luxuriant 

 wheat crops have been obtained for a number of consecutive years without 

 manure of any kind, simply by following out the TuUian system of stirring 

 up and pulverizing the soil ? 



How, too, are we to explain that capacity of subsisting without any artificial 

 supply of ammonia, which IMr. Lawes is led by his experiments to attribute 

 to turnips, and other plants of similar organization, unless we assume that 

 the power residing in the leaves of absorbing ammonia from the air may 

 render plants, in some cases at least, independent of any extraneous aid ? 



Be this, however, as it may, there is at least a wide distinction between 

 this opinion, and the one attributed to Baron Liebig by many, who would 

 seem to imagine, that according to his views, ammonia, if derived from arti- 

 ficial sources, was in a manner useless to vegetation. 



As if it could be a matter of any moment, whether the substance which 

 in both cases afforded the supply of nitrogen, and which in both cases also 

 was primarily derived from the decomposition of organic substances, had 

 been assimilated by plants directly upon its being thus generated, or had 

 been received into their system at a later period, after having been diffused 

 through the atmosphere 1 To suppose that Baron Liebig should have attached 

 any moment to this distinction seems inconsistent with many passages in 

 his work, in which, although the paramount importance of mineral manures 

 may be insisted upon, and the success which had in certain cases attended 

 the use of one compounded only of mineral ingredients may be put forward 

 as a motive for further trials, the utility of ammoniacal substances in all their 

 several forms is at the same time distinctly admitted. 



Still the practical question remains, whether, admitting the theoretical 

 truth of Baron Liebig's position, a larger expenditure of capital will not be 

 required for bringing a given farm into a condition to dispense with ammo- 

 niacal manures, than for procuring those materials which contain that ingre- 



