498 On the Grotcth of Barley by different Manures, Sfc. 



Taking together the results relating to the continuous growth 

 of barley in Hoos-field, given in former tables, and those here 

 given in Table XII., we have the means of comparing the produce 

 of barley obtained without manure during three years in suc- 

 cession, after a series of unmanured turnip crops, with that 

 obtained in the same seasons without manure, on land of very 

 similar intrinsic character ; but which, differed widely in the 

 condition induced by the very different cropping, &c., to which 

 it had been submitted. Next, confining attention to the results 

 of three years' barley after ten years' turnips (in Table XII.), we 

 have, taking the produce after the unmanured turnips as the 

 standard of comparison, the means of judging of the effects on 

 the succeeding barley, of an enormous excess of mineral manures 

 annually applied for the previous turnip crops. Compared with 

 the produce of barley obtained after this large residue of luineral 

 manures — by this time, no doubt, considerably distributed 

 through the soil — we can trace the increase due to any available 

 residue of nitrogen, where it was added in the different forms to 

 the mineral manures for the turnips. Lastly, by the effects of 

 the direct addition of nitrogenous manures for the barley (as in 

 Nos. 6 and 7), to the residual high mineral condition, we can 

 judge, whether or not, any deficiency of the crop on the other 

 plots was probably attributable to a want of available nitrogen 

 within the soil. 



If the characteristic influence of a rotation of crops, upon the 

 increased growth of the cereals, be at all materially due to the 

 elaboration in the soil, during the growth of other crops, of the 

 necessary mineral supplies for the white crop, it might surely be 

 expected that here, after ten meagre, unmanured crops of turnips, 

 appropriating no amount of silicates, we should have, if ever it 

 were possible, a large produce of barley, depending, with these 

 rich stores of prepared mineral food in the soil, upon atmospheric 

 sources for its nitrogen? If not after the many crops of un- 

 manured turnips, surely after those provided with a very large 

 excess of other mineral matters than silicates — the crop taking 

 none of the latter out — we should have enough elaborated and 

 conserved in tlie soil both of these and of all other mineral con- 

 stituents, to yield the fullest crop of barley which it is possible 

 to obtain by the conjoint influence of a very rich mineral condi- 

 tion of soil, and the normal season supplies of available nitrogen? 

 What is the result ? 



In the following Table (XIII.), is afforded a summary, view of 

 the produce of barley without manure for the three years in ques- 

 tion, in Hoos-field, devoted to the experiments on the continuous 

 growth of barley by different manures, side by side with that 



