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THE PRINCIPLES OF SOIL MANAGEMENT 



The disc plow is essentially a large revolving disc 

 set at such an angle that it cuts off and inverts the soil, 

 at the same time pulverizing it quite effectively after 

 much the same manner as the moldboard plow. One 



Fig. 135. Disc plow. 



advantage claimed for it is its lighter draft for the same 

 amount of work done, because it has rolling friction in 

 the soil instead of sliding friction. In practice, it appears 

 to be especially effective on very dry, hard soil and in 

 turning and covering rubbish.' 



338. Covering rubbish. The secondary function of 

 the plow is to cover weeds, manure and rubbish which 

 may be upon the surface. This also the turning plow 

 does very effectively. The cutting and turning of the 

 sod, rubbish and weeds is facilitated by several attach- 

 ments. These are: (1) Coulters. (2) Jointers. (3) Drag- 

 chains. There are several types of coulters. Blade 

 coulters are attached to the beam or to the share in such 

 a manner as to cut the furrow slice free from the land 

 side. They should be adjusted so as to cut the soil after 



