TILLAGE. 19 



than three or four inches. For clay land especially it 

 is better to harrow promptly after plowing if a crop 

 is to be soon sown. 



In recent years there has been a great increase in 

 the number a-nd variety of implements or machines 

 which, instead of pushing the soil about as does the 

 harrow tooth, cut it by means of blades or revolving 

 disks. For many purposes such implements are very 

 valuable. They pulverize the surface more effectually 

 than the harrow, and often loosen it to a greater depth. 

 They do not leave the surface smooth and level as 

 will a good harrow. They are being increasingly 

 used instead of the plow for preparing loose soils, 

 when comparatively free from stubble, for spring -sown 

 small grain crops. 



Boiling. — On many soils a good roller is one of 

 the most useful of farm machines. Used soon after 

 the land is plowed, when the surface is neither wet 

 hor thoroughly dry, it quite effectually breaks up clods 

 and tends to level and compact the surface. Rolling 

 cloddy, compact soils which have been plowed when 

 wet, may do some good, but the tendency is to push 

 the clods into the ground rather than to pulverize 

 them. Rolling light soils tends to check evaporation. 

 Seeds are often better covered if the land be rolled 

 after the seeds have been harrowed in. Rolling grass, 

 clover or small grain in the early spring often greatly 

 reduces injury from freezing and thawiag, as well as 

 makes the surface smoother for mowing. A roller of 

 large diameter is better for this last use; one of equal 

 weight but less diameter will be more effective in pul- 

 verizing the surface soil. 



Instead of rollers, many farmers use what may be 



