210 MANURE, ARTIFICIAL 



supply of constituents for organic formations, in addition to the mineral manures, that 

 we have found the use of alkalis not to be without effect. 



1 But it is at any rate certain that phosphoric acid, though it forms so small a pro- 

 portion of the ash of the turnip, has a very striking effect on its growth when applied 

 as manure ; and it is equally certain that the extended cultivation of root crops in 

 Great Britain cannot be due to the deficiency of this substance for the growth of 

 corn, and to the less dependence upon it of the root crops, as supposed by Baron Liebig. 



' These curious and interesting facts in relation to the growth of turnips, as well as 

 those which have been given in reference to wheat and to the leguminous crops, are suffi- 

 cient to prove how impossible it is to form correct opinions on agricultural chemistry 

 without the guidance of direct experiment in the field. And we are convinced that if 

 Baron Liebig had watched the experiments which we have had in progress during the 

 last eight years, he would long ago have arrived at conclusions in the main agreeing 

 with those to which we have been irresistibly led. 



' So much, then, for the results of experiments in the field, and for the considerations 

 In relation to the functional actions of plants, as bearing upon the character of the 

 manure required for their growth in a course of practical agriculture. Let us now 

 consider for a few moments what really are the main and characteristic features of 

 practical agriculture, as most generally followed in this country. 



' Let us suppose that the rotation adopted is that of Turnips, Barley, Clover, Wheat : 

 that the turnips and clover are consumed upon the farm by stock, and that the meat 

 thus produced, 40 bushels of barley, and 30 bushels of wheat, are all the exports from 

 the farm ; the manure from the consumed turnips and clover, and the straw, both of 

 barley and of wheat, being retained on the .farm. We have in this case, by the sale of 

 grain, a loss of minerals to each acre of the farm of only 20 to 24 Ibs. of potass 

 and soda, and 26 to 30 Ibs. of phosphoric acid, in the centre of the rotation, or an 

 average of 5 to 6 Ibs. of potass and soda, and 6| to 7 2 Ibs. of phosphoric acid per 

 acre per annum. In the sale of the animals there would of course be an additional 

 loss of phosphoric acid, though especially if no breeding-stock were kept, this would be 

 even much less considerable than in that of the grain ; and the amount of the alkalis 

 thus sent off the farm would, according to direct experiments of our own upon calves, 

 bullocks, lambs, sheep, and pigs, probably be only about one-fourth that of the phos- 

 phoric acid. It has, however, long been decided in practical agriculture that phos- 

 phoric acid maybe advantageously provided in the purchase of bones or other phospha- 

 tic manures, though in practice these are not found applicable as a direct manure for 

 the wheat crop ; and as we have already said, even when employed for the turnip, its 

 efficacy is not to be accounted for merely as supplying a sufficiency of that substance to 

 be stored up in the crop. 



' In conclusion, then : if the theory of' Baron Liebig simply implies that the grow- 

 ing plant must have within its reach a sufficiency of the mineral constituents of which 

 it is to be built up, we fully and entirely assent to so evident a truism ; but if, on the 

 other hand, he would have it understood that it is of the mineral constituents, as 

 would be collectively found in the ashes of the exported produce, that our soils are defi- 

 cient relatively to other constituents, and that, in the present condition of agriculture 

 in Great Britain, "we cannot increase the fertility of our fields by a supply of nitro- 

 genised products, or by salts of ammonia alone, but rather that their produce increases 

 or diminishes, in a direct ratio, with the supply of mineral elements capable of assimi- 

 lation," we do not hesitate to say that every fact with which we are acquainted, in 

 relation to this point, is unfavourable to such a view. We have before stated, how- 

 ever, that, if a cheap source of ammonia were at command, the available mineral con- 

 stituents might in their turn become exhausted by its excessive use.' 



MANURE, ARTIFICIAL. Agricultural writers usually divide manures into 

 two classes, natural and artificial. 



The first division includes farmyard manure, liquid manure, and the various com- 

 posts that are occasionally made by farmers from excrementitious matters, earth, 

 lime, and all sorts of refuse matters found or produced on the farm. 



In the second division we find guano, bone-dust, nitrate of soda, sulphate of 

 ammonia ; also the waste of slaughter-houses, night-soil, the refuse of glue-makers, 

 wool waste, and other refuse materials of certain factories; and likewise super- 

 phosphate of lime, blood manure, and a great .variety of saline mixtures, which are 

 now extensively manufactured in manure works, for the purpose of supplying 

 farmers with special chemical fertilisers, such as wheat-, barley-, oat-, potato-, flax- 

 manure, &c. The term artificial manure thus includes a great variety of different 

 materials, and is frequently applied to products which, like guano, are in point of fact 

 much more natural than farmyard manure, in the successful preparation of which a 

 certain amount of skill is required on the part of the farmer. The evident anomaly 

 of considering guano, bones, blood, and nitrate of soda (Chili saltpetre) as artificial 



