196 CROPS GROWN IN ROTATION 



It should be remembered that each of these three plots 

 was further subdivided into four quarter plots, in the first 

 place the third crop may be clover or a bare fallow, and 

 again the roots were carted off or fed on the land. Now 

 each plot is divided into two half plots, as the roots are carted 

 in all cases. 



The effect of the mineral manures without nitrogen is very 

 marked on the roots ; during the last seven courses the crop 

 averaged 201 cwt. per acre, as against 15 cwt. per acre only 

 on the unmanured plot. Table LXIV. shows that even on 

 the most impoverished of the quarter plots, that from which 

 the roots were always carted and where a bare fallow was 

 taken after the barley, the production amounted to 178 

 cwt. from 1884-1903, although the plot had been receiving no 

 nitrogen for thirty-six years previously, nor had any residues 

 of the previous crops, which would contain nitrogen, been 

 returned to the ground. Where the roots had been put back, 

 and where also a leguminous crop was taken in the rotation, 

 the crop amounted to 245 cwt., the increase being due to the 

 extra nitrogen thus returned to the soil. These results 

 illustrate the great dependence of the Swede crop upon a 

 plentiful supply of mineral, and especially of phosphatic, 

 manures ; the latter in particular seem to stimulate the 

 development of fibrous roots, thus enabling the plant to utilise 

 the resources of the soil. Again, the cultivation to which the 

 land is subjected for the Swede crop is calculated to nitrify 

 reserves of nitrogenous material in the soil and render the 

 plant more or less independent of a direct supply of nitrogen. 

 Thus, in ordinary farming practice with the land in good 

 condition the Swede crop only requires a small nitrogenous 

 dressing, but should always have a comparatively large amount 

 of phosphoric acid, in order to enable it to make the most of 

 the reserves in the soil and of the dung which is generally used 

 with this crop. 



The effect of the mineral dressing has been much less marked 

 on the barley than on the roots ; it has only increased the average 



