512 On the Groicth of Barley hy different Manures, ^-c. 



mineral constituents more than would happen under nearly a 

 century of ordinary rotation and home manuring. It has now- 

 been shown, that a very similar soil, certainly not more exhausted 

 in an agricultuial sense, gave an increase in the produce of barley,, 

 even on the first year's application of mineral manures. Collateral 

 experiments in the same field, as well as those in other fields of 

 very different, yet to a certain extent known history of relative 

 exhaustion or fertility, showed however, that mineral manures 

 were competent to yield, under these conditions of agricultural 

 exhaustion, but a small amount of increase when compared with 

 that obtained by nitrogenous manures. The evidence has also 

 led to the conclusion, that the mineral manures, if at all, yielded 

 increase in an extremely limited degree, unless there were avail- 

 able nitrogen accumulated by some means icitldn the soil ; in fact, 

 that the increase of produce, other things being equal, was more 

 in proportion to sucli available nitrogen within the soil, tlian to 

 any other supplied condition. It has, however, recently been 

 maintained in this Journal, that our characteristic nitrogenous 

 manures cannot be said to be active in proportion to the nitrogen 

 they contain. 



Thus Baron Liebig states (Journal of the Royal Agricultural 

 Society, vol. xvii. p. 298 ct seq.) that ammonia alone, or nitric 

 acid alone, has never been used in agricultural experiments ; and 

 he argues, that the acids in combination with ammonia in ammo- 

 niacal salts, and the bases in combination with nitric acid in the 

 nitrates, will have had their share in the results obtained by the use 

 of these salts; and that hence the value of such manures cannot 

 depend upon the amount of their nitrogen, but must depend on 

 the substances so combined with the nitrogen. 



Before going on to Baron Liebig's further illustrations and 

 arguments on the points here in question, it may be mentioned, in 

 reference to the above statements of fact, that we have ourselves, 

 as the reader is aware, used ammonia in combination with car- 

 bonic acid only, with very marked effects. Tlie late Mr. Pusey, 

 again, has given the account of his experiments in which nitric 

 acid, soda, and potash, were each separately used upon grass. 

 In reference to these experiments, Mr. Pusey says — " In botli 

 trials the nitric acid acted decidedly. The alkalies, neither of them, 

 produced even a trace of effect on the colour or on the growth of 

 the grass." And again — " The question being whether in saltpetre 

 the alkalies or the acid contained the active principle, we have 

 found upon a given sod the alkalies absolutely inoperative, while 

 the acid has acted exactly like saltpetre itself and like ammonia." 



It cannot for a moment be denied, that the state of combination 

 of the nitrogen in our nitrogenous manures, or their admixture with 

 other substances, has some share of influence on the result. We 



