170 



ELEMENTARY AGRICULTURE 



tlie disc. But 

 when hay fields 

 get too full of 

 weeds the best 

 way to fight 

 them is to ro- 

 tate the crop, 

 and plant 

 corn, potatoes, 

 rape, c a b - 

 bages or beets. 

 As these crops 

 require care- 

 ful cultivation 

 one can kill 

 the weeds and 

 at ^the same 

 time help 

 along a pay- 

 ing crop. 



Many weeds 

 mature on 

 corn or potato land or in stubble fields in the fall 

 after the crop has been taken off. This may be 

 prevented by following with a crop of winter oats, 

 rye, or crimson clover. 



Biennials such as burdock, wild carrot, and bull 

 thistle store up food in their roots the first year. 

 These are much harder to kill, but may be destroyed 

 by cutting the roots off below the crown. This is 



Fig. 92. Burdock 



