SOILS SUITABLE FOR CROP. 417 



ried on. And even on soils of such natural fertility as 

 these, great care is taken that their condition be not re- 

 duced by tillage cultivation previous to the woad crop, 

 for which it is generally the custom to hire rich pieces of 



ISATIS TINCTORIA Dyer's Woad. 



old pasture land for the intended period of the crop. On 

 the richest class of soils the crop may be profitably con- 

 tinued under cultivation for four years; three years, how- 

 ever, is the ordinary period, and even two successive crops 

 are considered enough to be taken from soils of an inferior 

 VOL. II. 60 



