HARROWING AND ROLLING IQ^ 



The value of this type of harrow as moisture 

 preservers depends on the manner in which they 

 are used. If the disks are so set that they cover 

 but a portion of the surface with a mulch of fine 

 earth they leave a ridge exposed to the action of 

 the wind and sun and the rate of evaporation is 

 greatly increased. The disks should be set at such 

 an angle that the whole surface shall be stirred or 

 covered. Soils which need the disk harrow should 

 generally be gone over again with some shallower 

 working tool to smooth the surface. An objection 

 to the rolling cutters is that unless great care is 

 taken they will leave the land in ridges and valleys. 



The two gangs of disks throw the earth in op- 

 posite directions. They are generally set to throw 

 it from the centre and the result is a shallow double 

 furrow the width of the machine. By lapping each 

 time the furrow is partially filled, but to get the 

 land smooth a smoothing harrow should be used 

 after the rolling cutter. 



Spring-toothed harrows (Fig. 55). Spring- 

 toothed harrows with their curved spring teeth 

 enter the soil readily, draw moderately easy and 

 pass over obstructions without much difficulty. 

 They are very useful in new land that is ''full of 

 roots and stumps and also stony land. They pul- 

 verize the soil to an average depth. They leave 

 the soil in ridges. The ridges can be leveled by a 

 smoother in the shape of a piece of plank attached 

 to the rear of the harrow. On newly plowed grass 

 land they tend to tear up the sod and leave it on 



