SOILS AND FERTILIZERS 



or they may be placed in an iron frame. A lever is 

 usually attached so that the spikes or teeth may be held 

 vertically, or they 

 may be made to 

 slant at any de- 

 sired angle back- 

 ward. This regu- 

 lates the depth to 

 which the spikes 

 enter the earth. 



A curved knife- 

 toothed harrow, 

 also called the FlG - 28 ' ~ s P rin s- tooth Harrow - 



Acme harrow, cuts and pulverizes the soil and is known 

 as a pulverizer. 



The spring-tooth harrow also pulverizes and culti- 

 vates the topsoil. It is often used in stony ground, or 

 ground in which stumps and roots of trees abound. 



When the tooth 

 catches on an 

 obstruction, it 

 springs back and 

 releases itself. 



The disk har- 

 row is a very 

 effective imple- 

 ment for pulver- 

 izing and loos- 

 ening up the 

 ground. The 

 disks cut the clods, and mix and push to one side the top- 

 soil. The two sets of disks are set at an angle, both sets 

 pushing the soil away from the center. This usually 



FIG. 29. Disk Harrow. 



