506 FIELD CROPS 



and disk land to clear it of weeds and then put on a new sup- 

 ply of weed seeds with the seed grain. The harrow or weed- 

 er may often be used in fields of drilled grain to destroy small 

 weeds during the first few weeks of spring. The harrowing 

 should be done with the drill rows rather than across them. 



Figure 165. Blossom and root of wild mustard; also (1) the ripe seed pod; (2) 

 the blossom, and (3) the seeds. 



Harrowing broadcast grain will help to keep down weeds, 

 but it will also reduce the stand of grain. Ragweed and other 

 weeds which come up in grain fields after harvest may be 

 prevented from seeding by mowing them when they first 

 come into bloom, by pasturing, preferably with sheep, or by 

 disking the land. 



Among the common weeds of grain fields are wild oats, 

 wild garlic, wild mustard, Frenchweed, peppergrass, smart- 

 weed, Russian thistle, knot weed, wild morning-glory, corn 

 cockle, milkweed, marsh elder, ragweed, kinghead, Canada 

 thistle, and sow thistle. 



