TILLAGE 



669 



about from 30° to 40° with the horizontal. A furrow thus 

 set furnishes ready entrance for rain water and facilitates 

 the best of aeration for the soil. Such an angle is espe- 

 cially to be recommended for turning under green manures. 

 The capillary connections with the subsoil are not broken 

 and the green material is well distributed from the top 

 to the bottom of the furrow. Where a sod is to be plowed, 

 a flatter turning of the furrow is advocated in order to 

 increase the packing and avoid the danger of the sod's 

 interfering with subsequent cultivation. 



Fig. 69. — Section of plowed land showing the correct proportions and 

 position of the furrow slice as left by a moldboard plow. The effect 

 of the jointer in turning under the edge of the furrow slice as well 

 as the position of turned under vegetation is apparent. 



574. Depth and width of furrow. — There is a general 

 relation between the width of the furrow slice and its 

 depth. In general, it may be said that this ratio is about 



