TILLAGE 



335 



degree of effectiveness, however, may be increased or diminished bv 

 adjusting the angle of the disk with the direction of movement. 

 Next to the plow the disk is one of the most important and useful 

 implements. It may he used very effectively before the plowing is 

 done, and is one of the host tools for the preparation of a seed bed. 

 Either the solid disk or the cut-away may be used to excellent 

 advantage in cutting up corn-stalks and other vegetable material 

 and mixing them with the soil before plowing. This insures the 

 close contact of the furrow-slice with the soil beneath. A small 

 rotary spading harrow is sometimes attached to the plow. 



I in. 1")1. Smooth or drum roll(r. 



3. Compacters. Compacting is necessary because most of out- 

 crops require a firm but mellow seed bed. In manv cases in our 

 heavier soils clods are formed which require the use of the roller 

 to crush, while in the case of sands, sandy loams, and many silt, 

 loams the soils are so loose that root development and moisture 

 retention are interfered with. In arid and semi-arid regions the 

 subsurface compacter is used to prevent the excessive loss of moist- 

 ure through any large air spaces that may exist in the soil. The 

 packing also increases upward capillary movement of soil moisture. 

 and consequently less water is lost by the downward movement. 



The smooth or drum roller (Fig. 1-">1) is used quite exten- 



