WEEDS IN CULTIVATED FIELDS 



535 



With some intertilled crops, the first two or three culti- 

 vations can be given very rapidly and cheaply with the har- 

 row or weeder. Later cultivations should be with tools that 

 stir the surface soil sufficiently to kill small weeds and main- 

 tain a dust mulch. Weeds that come up in the row should be 

 hoed or pulled out if necessary, though they may often be 

 destroyed when small by 

 covering them with 

 earth in cultivating. 

 Cultivation should be 

 continued as long as 

 possible without injury 

 to the growing crop, 

 or until the ground is 

 completely shaded. 

 Poor cultivation, especi- 

 ally on fields that are 

 infested with perennial 

 weeds, is often worse 

 than none at all, as it 

 simply serves to spread 

 the weeds. Among the 

 most common weeds of 

 cultivated crops are nut 



grass, Johnson grass, 



Fig. 159. Wild buckwheat or knotweed, 

 towing the way in which it twines around 

 with which it is growing. 



foxtail, crabgrass, quack c 



grass, knotweed, morning glory, velvet weed, milkweed, 



Canada thistle, sow thistle, ragweed, and kinghead. 



707. Weeds of Grain Fields. In wheat, oat, barley, 

 and other small grain fields, less opportunity is afforded for 

 the destruction of weeds than in cultivated crops. Here 

 most of the work must be done before the seed is sown. The 

 same kind of preparation, so far as possible, should be given 



