34 On Agricultural Chemistry. 



Thirdly, that with a very liberal supply of potash with some 

 soda and magnesia also, in addition to superphosphate of 

 lime. 



Years. 



Plot 



continuously Un- 

 manured. 



Plot 



with Superphosphate 

 of Lime alone every 

 Year. 



Plot 



with Superphosphate 

 of Lime and mixed 

 Alkalies. 



1843 

 1844 

 1845 

 1846 

 1847 

 1848 

 1849 

 1850 



Tons, cwts, qrs. lbs, 

 4 3 3 2 

 2 4 10 



. . 13 2 24 



Tons. cwts. qrs. lbs, 



12 3 2 8 



7 14 3 0 



12 13 3 12 



1 18 0 0 



5 11 0 1 



10 11 0 8 

 3 15 0 0 



11 9 0 0 



Tons. cwts. qrs. lbs. 



11 17 2 0 

 5 13 2 0 



12 12 2 8 

 3 10 1 20 

 5 16 0 0 

 9 14 2 0 

 3 13 2 8 

 9 7 1 12 



Totals. 



Means . 



65 16 1 1 



62 5 1 20 



7 15 2 20 



It is seen then, that in the third season, viz. 1845, the produce 

 of the unmanured plot is reduced to a few hundredweights, and 

 since that period the size of the bulbs has been such that they 

 have not been considered worth weighing. On the other hand, on 

 the plot with superphosphate of lime alone for eight successive years, 

 we have an average produce of about 8^ tons of bulb ! varying, 

 however, exceedingly, year by year, according to the season. We 

 see, too, that by the addition to superphosphate of lime of a 

 large quantity of the alkalies, much greater than could be taken 

 ofF in the crop, the average produce is not so great by nearly 

 half a ton as by the superphosphate of lime alone. It must be 

 admitted that this extraordinary effect of superphosphate of lime 

 cannot be accounted for by the idea of merely supplying in the 

 actual constituents of the crop, but that it is due to some special 

 agency in developing the assimilative processes of the plant. This 

 opinion is favoured by the fact that in the case where the super- 

 phosphate of lime is at once neutralized by alkalies artificially 

 supplied, the efficacy of the manure would seem to be thereby 

 reduced. And from this again, we would gather that the effect 

 of the phosphoric acid as such, cannot be due merely to the libe- 

 ration within the soil of its alkalies, or we should suppose that 

 the artificial supply of these would at least have been attended 

 with some increase of produce. But this is not the case, not- 

 withstanding that by means of superphosphate of lime alone 

 there has been taken from the land more of the alkalies in 

 which the ash of the turnip so peculiarly abounds, than would 

 have been lost from it in a century under the ordinary course 



