CULTIVATION. 



201 



usually follows the surface plow, tutering the soil to 

 the depth of from eight to fifteen inches below the 

 bottom of the surface furrow. 



The best pattern now made (the steel sub-soil 

 plow) is represented in the following figure. 



Fig. 6. — Wrought Iron and Steel Sub -soil Plow. 



The sub-soil plows first made raised the whole soil 

 about eight inches, and required very great power in 

 their use, often six or eight oxen. The implement 

 shown in the figure, raising the soil but slightly, may 

 be worked with much less poAver, and produces 

 equally good results. It may be run to a good 

 depth in most soils by a single yoke of oxen. 



The motion of any part of the soil which is effected 



by this sub-soil plow is very slight, but it is exerted 



throughout the whole mass of the soil above the 



a* 



