678 SOILS: PROPERTIES AND MANAGEMENT 



In this particular it may be considered as belonging to the 

 third set of implements, the clod crushers. But as com- 

 pared with the roller on hard soil it is more efficient. 



582. Seeder cultivators. Many implements used 

 primarily for seeding purposes are also cultivators, and 

 their use is equivalent to cultivation. The grain drill 

 is a good example of this group. It is essentially a culti- 

 vator either shoe or disk adapted to depositing the 

 grain in the soil at the proper depth. All types of planters 

 that deposit the grain in the soil have a similar action 

 on the structure of the soil. The ordinary two-row maize 

 planter, the potato planter, and the like, while of low 

 efficiency as cultivators, still have an effect which is 

 measurable. This action is well seen in the lister, used 

 for planting maize, by which the grain is deposited beneath 

 the furrow, which is filled by cultivation after the grain 

 is up. The lister is generally used without previously plow- 

 ing the ground, and its use is limited to regions of low rain- 

 fall where the soil is aerated by natural processes. Plowed 

 ground listers have lately been introduced, which com- 

 bine the advantages of deep planting with proper prep- 

 aration of the soil. 



There is also a very considerable tillage action in many 

 harvesting implements. The potato digger, for example, 

 very thoroughly breaks up and cultivates the soil, and 

 this process is one important reason for the general 

 high yield of crops following the potato crop. Bean 

 harvesters and beet looseners also have a similar action 

 on the soil. 



583. Packers and crushers. These may be divided 

 into two groups those implements that aim to compact 

 the soil, and those the primary purpose of which is to 

 pulverize the soil by crushing the lumps. Both kinds 



