472 THE PRINCIPLES OF SOIL MANAGEMENT 



board, and a depth of furrow slice, which are calculated 

 to give the best results. This fact is to be kept constantly 

 in mind in plowing soil. Sod land requires a different 

 shape of plow from fallow land, sandy land from clay 

 land. Rubbish on the surface may be handled by one 

 plow and not by another. Wet clay should have the 

 use of a different shape of plow from dry soil. 



There are several different shapes of plow. Among 

 these the most prominent types are the moldboard, 

 the disc, the hillside and the subsoil. 



Of the moldboard type there are two general shapes : 



(1) The long, sloping moldboards, with little or no over- 

 hang, found on what is called the sod plow. This neatly 

 cuts off the roots at the bottom of the slice, and slowly 

 and gradually twists the soil over without breaking the 

 sod, and lays it smoothly up to the previous furrow- 

 slice. It is seldom desirable to completely invert the 

 soil. According to depth of plowing, the furrow-slice 

 should be laid at an angle with the horizontal of from 

 25 to 50, so that the projecting edge of the slice may 

 be worked down for a seed-bed, while the roots and 

 rubbish on the surface is somewhat uniformly distri- 

 buted through a considerable depth of soil, instead of 

 occupying a single layer in the bottom of the furrow. 



(2) The short, steep moldboard with a marked overhang. 

 This is not adapted to sod land, because it breaks up 

 the sod and shoots it over in a rough, jagged manner 

 with uneven turning. But on fallow land, to which it 

 is adapted, it very completely breaks up the soil and 

 throws it over in a nearly level mellow mass. The pul- 

 verizing effect is obviously much greater than with the 



