208 MANUEE 



the apparent luxuriance of the crop is greater, and the produce of straw really heavier, 

 by spring rather than autumn sowings of Peruvian guano and other ammoniacal 

 manures, yet we believe that that of the corn will not be increased in an equivalent 

 degree. Indeed, the success of the crop undoubtedly depends very materially on the 

 progress of tho underground growth during the winter months; and this again, other 

 things being equal, upon the quantity of available nitrogenous constituents within the 

 soil, without a liberal provision of which, the range of the fibrous feeders of the plants 

 will not be such as to take up the minerals which the soil is competent to supply, and 

 in such quantity as will be required during the after-progress of the plant for its 

 healthy and favourable growth. 



' The next result to be noticed is that obtained on plot 6, now also divided into two 

 equal portions, designated respectively &a and 66. Plot No. 6 had for the crop of 1844 

 superphosphate of lime and the phosphate of magnesia manure, and for that of 1845 

 superphosphate of lime, rape-cake, and atomoniacal' salts. For this the third experi- 

 mental season, it was devoted to the trial of the wheat-manure manufactured under 

 the sanction of Professor Liebig, and patented in this country. 



' Upon plot 6a, 4 cwts. per acre of the patent wheat-manure were used, which gave 

 20J bushels, or rather more than two bushels beyond the produce of the unmanured 

 plot ; but as the manure contained, besides the minerals peculiar to it, some nitrogenous 

 compounds, giving off a very perceptible odour of ammonia, some, at least, of the in- 

 crease would be due to that substance. On plot 6b, however, the further addition of 

 1 cwt. each of sulphate and muriate of ammonia to this so-called ' mineral manure' 

 gives a produce of 29^ bushels. In other words, the addition of ammoniacal salt to 

 Liebig's mineral manure has increased the produce by very nearly 9 bushels per acre 

 beyond that of- the mineral manure alone, while the indrease obtained over the un- 

 manured plot by 14 tons of farmyard manure was only 9^- bushels. 



'If, then, the "mechanical form and chemical qualities" of the so-called "mineral 

 manure " were at fault, the sulphate of ammonia has, at least, compensated for the 

 defect ; and even supposing a mineral manure, founded on a knowledge of the compo- 

 sition of the ashes of the plant, be still the great desideratum, the farmer may rest 

 contented, meanwhile, that he has in ammonia, supplied to him by Peruvian guano, 

 by ammoniacal salts, and by other sources, so good a substitute. 



' It surely is needless to attempt further to justify, by the results of individual 

 years, our assertion, that in practical agriculture nitrogenous manures are peculiarly 

 adapted to the growth of wheat. "We shall therefore conclude this part of our subject 

 by directing attention to the history of a few of the plots throughout the entire series 

 of years, as compared with that of the unmanured plot during the same period. 



'In support of the view that leguminous plants do possess a superior power of 

 reliance upon the atmosphere for their nitrogen, and, indeed, that it is to this pro- 

 perty that they materially owe their efficacy in rotation with grain, we may refer 

 to the admirable investigations into the chemistry of agriculture of M. Boussingault. 

 His experiments, however, have not received the attention which they merit from the 

 agriculturists of this country ; probably on account of the small amounts of produce 

 which he obtained. But it must be remembered that his investigation had for its object 

 to explain the practices of agriculture as he found them in his own locality, before 

 attempting to deviate from its established rules. M. Boussingault states the rotation 

 usually adopted at Bechelbronn, and throughout the greater part of Alsace, to be as 

 follows: 



"Potatoes or beet-root;" "Wheat;" "Clover;" "Wheat;" 



and that the average of wheat so obtained is, after potatoes 19 bushels, after beet-root 

 17 bushels, and after clover 24 bushels. Now we find by reference to his table that the 

 first crop of wheat, grain, and straw removed 17 Ibs. of phosphoric acid and 24 Ibs. of 

 potash and soda ; the following clover crop, 18 Ibs. of phosphoric acid and 77 Ibs. of 

 potash and soda ; and after this removal of alkalis and phosphates by the clover, 

 a larger crop of wheat is obtained. Surely it would seem impossible to reconcile this 

 result with a theory which supposes the produce of wheat to rise and fall with the 

 quantity of minerals available within the soil. If, however, we admit that the first 

 crop of wheat could not take up the mineral matters existing in the soil for want of 

 nitrogenous supply, and that tho clover crop, not being so dependent upon supplied 

 nitrogen, was able to take up the minerals required for its growth, and that it more- 

 over left in the soil sufficient ammonia or its equivalent of nitrogen in some form, to 

 give the increased crop of wheat, we have a much more consistent and probable solu- 

 tion of the results. There is little doubt that M. Boussingault could have increased 

 his produce of wheat by means of ammoniacal salts : whether he could have done so 

 economically is another question, depending of course upon the relative prices of grain 

 and ammonia. 



