336 



SOIL PHYSICS AND MANAGEMENT 



sively, but is not as effective as some other forms and is gradually 

 being replaced. When used for crushing clods these are frequently 

 pressed into the soil without being affected to any extent, and a 

 subsequent harrowing before a rain usually brings them to the sur- 

 face again. Its use greatly increases evaporation of moisture. 



FIQ. 



Iti-packer, a form of corrugated roller, showing the work done. 



iflil'A '1 J|B 



fc^M&t ' 



*^ " 



Fio. 153. Disk drill and its work. 



Corrugated Roller. The smooth form of roller is gradually 

 being displaced in the corn belt by the culti-packer or corrugated 

 roller (Fig. 152), which consists of a series of wheels with a sharp 

 ridge about two to two and one-half inches in height. This imple- 

 ment is much more effective in crushing clods and leaves the ground 

 covered with a thin mulch. 



