HOCKINGS' GARDEN MANUAL, 



18 



ROTATION OF CROPS. 



Certain plants exhaust the soil of the particular 

 salts or other mineral matters which are required for 

 their nourishment. When the substance required by 

 plants is found in the soil in which they grow, the 

 plants are vigorous ; but when the soil becomes ex- 

 hausted of them the plants become weak and sickly, 

 and a further crop of that plant cannot be grown in 

 that soil until it has had returned to it the substance 

 which had been exhausted. Another crop, however, 

 requiring a different substance may be grown in the 

 same soil the next year. For instance, plants that 

 require potash, such as the beet, the mangel wurzel, 

 and the turnip, may succeed plants that require lime, 

 such as beans, peas, &c. 



