266 SOILS AND FERTILIZERS 



dressings of potash and phosphoric acid are admissible. 

 When sugar beets follow corn which has been manured, 

 or grain which has left the soil in an average state of 

 fertility, and a medium dressing of commercial fertilizer is 

 applied, the food requirements of the crop are well met. 



317. Roots. Mangels are gross feeders and re- 

 move a larger amount of fertility from the soil than 

 any other farm crop. 74 When fed to stock and the 

 manure is returned to the soil, they materially aid in 

 making the plant food more available for delicate- 

 feeding crops. Mangels are better able to obtain phos- 

 phoric acid than are turnips and need the most help 

 in the way of nitrogen. Turnips are surface feeders 

 with stronger power of nitrogen assimilation than the 

 grains, but with restricted power of phosphate assimi- 

 lation. Manures for turnips should be phosphatic in 

 nature. 



318. Rape is a type of strong feeding plant capa- 

 ble of obtaining its food under conditions adverse to 

 grain crops. When grown too frequently upon the 

 same soil, it does not thrive. On account of its great 

 capacity for obtaining food, it is a valuable crop to 

 use for green manuring purposes. 80 Farm manure is 

 the most valuable fertilizer for rape. 



319. Buckwheat is a strong feeding crop, and its 

 demands for food are easily met. On rich soil, a rank 

 growth of straw results, with poor seed formation. 



