TILLAGE MACHINERY 83 



121. The disk harrow. This tool is perhaps the best 

 adapted for pulverizing and loosening the ground of any 

 yet devised. On account of its rolling action, it can be 

 used for a great variety of conditions. It does excellent 

 service in reducing plowed ground which is inclined to 

 be soddy, and may even be used to prepare hard and dry 

 soils for plowing. It may also be used to advantage in 

 destroying weeds after they have grown beyond the con- 

 trol of the smoothing harrow. In fact, the disk harrow 

 should be in use on every farm. 



FIG. 55 A TWO-LEVER DISK HARROW. SCRAPERS OPERATED BY THE FEET 



122. The full-bladed disk harrow. This class of har- 

 row may be used to good advantage as a pulverizer, and 

 the blades are easily sharpened when dull, either by 

 grinding or turning to an edge. The diameter of the disks 

 may vary from 12 to 20 inches. For general purposes, 

 the medium-sized, or 14- or i6-inch, disk is the size best 

 adapted, although the larger sizes may have slightly less 

 draft. The penetration of the disk blades into the ground 



