ROTATION OF CROPS 205 



the object would be attained by growing 

 Italian rye-grass, or some other non-legu* 

 minous fodder crop ; but, of course, under 

 this system the land would not be periodically 

 enriched with nitrogen. 



The Norfolk four-course shift has not 

 attained to its present position of import- 

 ance without resting upon a solid foundation 

 of advantages, cultural and otherwise, which 

 may be summarized as follows : The two 

 principal cereal crops, barley and wheat, are 

 sowed at different times of the year, which 

 is convenient from the point of view of the 

 economical utilization of labour; moreover, 

 they differ in the character of their root- 

 system, barley feeding chiefly on the surface 

 layers of the soil, whereas wheat penetrates 

 deeply into the subsoil. Then, again, it is 

 found that wheat grows well after clover, 

 utilizing very fully the nitrogen stored up in 

 the root-residues, and finding congenial con- 

 ditions of growth in the compact clover sod. 

 The clover crop, also, being removed from 

 the land not later than July, permits of the 

 ground being ploughed sufficiently early to 

 admit of wheat being sowed at the best time 

 of year early autumn. It may be men- 

 tioned that, if the land is not sufficiently 

 clean, it may be broken up directly the clover 



