152 



TILTH AND TILLAGE 



disk harrow is frequently used on fields infested with quack grass, 

 to bring the roots to the surface. It is always best to lap the disk 



Fia. 91. A spading disk. 



FIQ. 92. The smoothing harrow. (Drag.) 



harrow half to get best results in pulverizing fall plowed lands, sod 

 or lumpy soil except when two disk harrows are used in tandem. 

 The degree of pulverization depends upon the angle at which the 

 disks are set. 



