EOOT CEOPS 79 



tion, and thus supply the necessary organism. On 

 soils long cultivated such treatment is seldom success- 

 ful. Apart from the tubercles, leguminous plants are 

 nourished in the ordinary way through their root-hairs, 

 and a deeply-rooted plant, like red clover or lucerne, 

 obtains considerable food supplies from the subsoil. 



Except in the case of extraordinary rich soils, land 

 loses the power of growing most leguminous plants by 

 repeated cropping with them, and is said to be " clover 

 sick "or "bean sick." The origin of this barrenness 

 has not yet been satisfactorily explained ; it is gener- 

 ally intensified by an attack from insects on the weak- 

 ened plant. No means of remedying this condition is 

 known save by the growth of other crops for several 

 years. 



Potash manures and superphosphate have generally 

 a very beneficial effect upon leguminous crops ; they 

 fail, however, to cure clover sickness. Farmyard 

 manure, gypsum, and lime are also serviceable. 



Root Crops. — All these crops contain a large amount 

 both of nitrogen and ash constituents ; among the 

 latter potash greatly preponderates. Turnips contain 

 more sulphur than any other farm crop. 



Turnips and sioedcs draw their food chiefly from the 

 surface soil. The land receives an abundant tillage 

 before sowing the seed, and the crops are hoed after- 

 wards ; they remain also in possession of the soil till 

 the end of autumn. Under these circumstances they 

 display a great power of taking up nitrogen from the 

 soil. Turnips are also well able to supply themselves 

 with potash when growing in a fertile soil, but they 

 have singularly httle power of appropriating the com- 



