THE TILLAGE OP THE SOIL 60 



or pulverize the land to a great depth, the sub- 

 soil plow is run in the furrow behind the ordi- 

 nary plow. Subsoiliug provides a deeper bed 

 for roots, breaks up the hard-pan, and dries the 

 soil. More permanent results are usually ob- 

 tained by thorough under-drainage. 



36. By surface-working tools 



98. Tillage by means of surface-working 

 tools as hoes, rakes, cultivators, harrows, clod- 

 crushers has the following objects : (a) to 

 make a bed in which seeds can be sown or plants 

 set, (b) to cover the seeds, (c) to pulverize the 

 ground, (d ) to establish and maintain an earth- 

 mulch, (e) to destroy weeds. Aside from these 

 specific benefits, surface tillage contributes to 

 the general betterment of soil conditions, as 

 outlined in 87, 88, 89. 



99. In making the earth -mulch (the im- 

 portance of which as a saver of moisture is 

 fully explained in 82, 83), the other objects of 

 surface tillage are also secured ; therefore we 

 may confine our attention to the earth-mulch for 

 the present. The mulch is made by shallow 

 tillage about three inches deep, in field condi- 

 tions before the seeds are sown. The first til- 

 lage after plowing is usually with a heavy and 

 coarse tool, as a clod-crusher, cutaway harrow, 



