Forms of Plows. 241 



use the less steep mold board and plow as shallow as other 

 conditions will allow. 



If a soil has become a little too dry and is not pulverizing 

 fine enough, use the steeper mold board and plow deep for 

 this will split it into thinner layers, make the soil finer, 

 and the tilth better. 



299. The Kind of Soil, the Shape of the Mold Board, and 

 the Draft of the Plow. Since the steepest mold board bends 

 the furrow slice most and pulverizes most, it is clear that 

 the work done is greatest, and hence that the draft will be 

 most. 



Since deep plowing pulverizes more than shallow plow- 

 ing the work done is more than in proportion to the depth. 



Since clay soils have more and larger granules which 

 must be sheared in two in plowing than sandy soils do, the 

 labor of plowing must be greater. 



Since the granules of the soil are not as strong when the 

 soil is moist as when dry it plows much easier, when in 

 good condition. But if the soil has become too dry and yet 

 must be plowed, it should be plowed deeper rather than 

 shallower. This is necessary to pulverize better, to get 

 more moist soil on the surface for the immediate seed bed, 

 and to quicker moisten and bring into condition the layer 

 which has become too dry. 



300. The Sod Plow The sod or breaking plow is con- 

 structed so as to reduce the draft as much as possible by 

 doing only the work needed to cut and turn over the fur- 

 row slice. This is accomplished by making the mold board 

 very long and slanting so that the furrow slice is bent and 

 twisted as little as possible, as shown in Fig. 77 ; the chief 

 work being to cut it and roll it bottom up. 



The extremely oblique edge of the share in the breaking 

 plow reduces the draft, in cutting off the roots by allowing 

 the cutting to be done gradually and with a drawing cut, 

 just as it is easier to cut off a limb by letting the blade of 

 the knife slant backward, drawing it across. 



