J>R. DAUBENY ON THE ROTATION OF CROPS, ETC. 243 



In another of the beds which had reared a permanent crop, viz. that of potatoes, 

 the proportion of the phosphates, alkalies, and magnesia did not appear to vary much, 

 the analysis of 1000 grains of the finer portion sifted, affording the following results : — 



Phosphate of lime . . . 0*86 



Potass 157 



Soda . 0*27 



Magnesia 0*82 



The organic matter here was 53'00 



A third of the beds in the same garden, which had borne a crop of turnips for ten 

 years, exhibited rather a remarkable anomaly, as the phosphates exceeded in quantity 

 considerably that present in the contiguous garden, the results being as follows :-- 



Potass, in 1000 parts . . 0'46 

 Soda ....... 0*74 



Phosphate of lime . . . 1*62 

 Organic matter . . . 1 10*80 



It will be seen, that the permanent crop of turnips in ten years would have extracted 

 from the soil only 0*36 of phosphoric acid, whilst the barley in the same time had 

 extracted 1-84, and the potatoes .0*80 ; hence perhaps the difference in the quantity 

 present in the soil. 



One only of the plots of ground, which had grown a succession of different crops 

 for ten years without manure, was examined *", and the proportion of the above 

 ingredients found in it appeared to be as follows, viz. — ■ 



Potass in 100 grains . . 1*96 



Soda 1-J2 



Phosphate of lime . . . 0*33 

 Organic matter .... 76*50 



It will be seen from the table in the following page, that, taking as our standard 

 the composition of the contiguous garden, of which the analysis is first reported, and 

 in which the proportion of phosphoric acid would seem to be lower than it is in most 

 of the plots of ground experimented upon, even after ten years' cropping without 

 manure (judging from the few which were examined), a sufficient quantity of the 

 above ingredient existed, to supply what would be necessary for nineteen crops of 

 barley, of the same amount as the average of those obtained from the permanent bed, 

 and of the same quality as that produced in 1844. 



* The crops were, barley in 1844, hemp in 1843, buckwheat in 1842, tobacco in 1841, parsley in 1840 and 

 1839, mint in 1838 and 1837, parsley in 1836, and beans in 1835. 



MDCCCXLV. 2 K 



