328 SOIL PHYSICS AND MANAGEMENT 



The stubble plow (Fig. 138C) has a short, strongly curved 

 mold-board and is probably the best form to use in old land. In 

 general the more curvature or twist there is to the mold-board the 

 greater the pulverization, the better is the condition of the soil after 

 plowing, provided it has the proper moisture content. This plow 

 is not desirable to use in breaking sod, because of the rough con- 

 dition in which it leaves the surface. The jointer is sometimes used 



Fio. 139. Plow with separate jointer and rolling coulter attached ready for use. (Moline 



Plow Company.) 



in the plowing of light sods, as it materially aids in turning under 

 and preventing the further growth of grass (Figs. 139 and 140). 



The general purpose plow (Fig. 138B) is a form intermediate 

 between the stubble and sod plows in length and curvature of mold- 

 board. It may be used for either stubble or sod. It does not pul- 

 verize the soil so thoroughly as the stubble mold-board, and as a con- 

 sequence it leaves sod in much better condition for working into 

 a good seed bed. For all uses it is probably the best. 



