TYPES OF PLOWS 



475 



mental to the circulation of air and moisture and inter- 

 feres with the penetration of plant roots. Consequently, 

 occasional deep plowing or even subsoiling is recom- 

 mended to break up this unfavorable soil structure, 

 commonly called the " plow sole." There is less tendency 

 for the disc than the moldboard plow to form the "sole." 

 The hillside plow is a modified form of the mold- 

 board plow, which has a double curvature to the mold- 

 , board, so that it is essentially two plows in one. This 

 swings on a swivel 

 in such a way that 

 it may be locked 

 on either the right 

 or the left side. It 

 removes the neces- 

 sity of plowing in 

 beds, and, by per- 

 mitting all of the work to be done from one side, enables 

 the plowman to lay the furrow slices in one direction. 

 On the hillside this direction is down the slope, because 

 of the greater ease in turning the soil in that direction. 

 It also removes the difficulty of pulling up and down the 

 hill. There is another type of compound moldboard 

 plow designed to eliminate "dead furrows" and "back 

 furrows." The former is developed by turning the last 

 furrow slices of two lands in opposite directions, thereby 

 leaving a gulley between which, by reason of its fre- 

 quent unproductive character, is termed the "dead 

 furrow."' The back furrow consists of two furrow slices 

 thrown together, usually forming a ridge more productive 

 than the average of the land. 



Fig. 134. Berry hoe or ridger. For close tillage 

 of berries, vines and low-headed trees. 



