X.] CAN ROTA TIONS REP LA CE PER TILISERS ? 29 \ 



particular crop is grown continuously on the same land. 

 On the rotation field at Rothamsted the yield of 

 wheat on the unfertilised plot has been remarkably 

 maintained ; for the last five courses (loth to 14th of 

 the whole series) it has averaged 26-2 bushels per acre, 

 but it is below the yield of the fertilised plots on the 

 Broadbalk field, which averaged 35-7, 32, and 39-7 

 bushels for the same years, and also below the fertilised 

 plot on the same rotation field, which averaged for the 

 same period 37-1 bushels per acre, although the fertiliser 

 is only applied once in four years to the Swedes, which 

 are followed by barley and either clover or a bare fallow 

 before the turn of the wheat comes round. But with 

 other crops than wheat no such maintenance of yield is 

 to be seen on the unfertilised plot of the rotation field — 

 the barley yield has been reduced to 15-8 bushels 

 against 27-7 on the fertilised plot, the clover yield to 

 94 cwts. against 37-8 on the fertilised plot, and the 

 turnips to as little as 16 cwts. against 400 on the 

 fertilised plot. Here we see that with the barley, clover, 

 and particularly with the turnip crop, a rotation is quite 

 unable to do the work of the fertiliser ; the yield of 

 turnips is reduced to a minimum on the impoverished 

 soil, even though the crop only comes round once in 

 four years and then grows so poorly that it can do little 

 specific excretion to harm the succeeding crop. Many 

 instances could be given of the incapacity of certain 

 plants to grow in soil the fertility of which had been 

 exhausted by other crops ; for example, at Rothamsted 

 in 1903, Swede turnips were sown on Little Hoos field, 

 which was known not to have been cropped with Swedes 

 or any kindred crop for more than forty years, and the 

 average yield from thirty-two unmanured plots was only 

 9-3 tons per acre, although an exceptionally good start 

 was made by the plant. In the following season barley 



